When loading some chunks, that were previously generated, the server randomly crashed (a few times).
Restarting the server made the game continue as normal, so it doesn't happen multiple times for the same chunk.
There's nothing special in the chunks, just some colored terracotta and (infested) stone mainly; no entities.
---- Minecraft Crash Report ----
// Surprise! Haha. Well, this is awkward.
Time: 3-5-18 13:45
Description: Exception ticking world
java.lang.NullPointerException: Exception ticking world
at sh.o_(SourceFile:418)
at sh.k_(SourceFile:216)
at net.minecraft.server.MinecraftServer.w(SourceFile:696)
at rs.w(SourceFile:367)
at net.minecraft.server.MinecraftServer.v(SourceFile:629)
at net.minecraft.server.MinecraftServer.run(SourceFile:534)
at java.lang.Thread.run(Unknown Source)
A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------
-- Head --
Thread: Server thread
Stacktrace:
at sh.o_(SourceFile:418)
at sh.k_(SourceFile:216)
-- Affected level --
Details:
Level name: medabots_server
All players: 1 total; [sj['FVbico'/13, l='medabots_server', x=-1489,98, y=109,07, z=485,14]]
Chunk stats: ServerChunkCache: 1217 Drop: 0
Level seed: 64
Level generator: ID 01 - flat, ver 0. Features enabled: false
Level generator options: {"flat_world_options":"minecraft:bedrock,49*minecraft:stone,4*minecraft:dirt,minecraft:grass_block;4;"}
Level spawn location: World: (11,54,-38), Chunk: (at 11,3,10 in 0,-3; contains blocks 0,0,-48 to 15,255,-33), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
Level time: 67135918 game time, 6000 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 1 (now: false), thunder time: 1 (now: false)
Level game mode: Game mode: adventure (ID 2). Hardcore: false. Cheats: false
Stacktrace:
at net.minecraft.server.MinecraftServer.w(SourceFile:696)
at rs.w(SourceFile:367)
at net.minecraft.server.MinecraftServer.v(SourceFile:629)
at net.minecraft.server.MinecraftServer.run(SourceFile:534)
at java.lang.Thread.run(Unknown Source)
-- System Details --
Details:
Minecraft Version: 18w16a
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_161, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 1541178888 bytes (1469 MB) / 2061500416 bytes (1966 MB) up to 2061500416 bytes (1966 MB)
JVM Flags: 2 total; -Xms2G -Xmx2G
Profiler Position: N/A (disabled)
Player Count: 1 / 100; [sj['FVbico'/13, l='medabots_server', x=-1489,98, y=109,07, z=485,14]]
Data Packs: vanilla, file/Medabots Server (incompatible)
Is Modded: Unknown (can't tell)
Type: Dedicated Server (map_server.txt)
Note: some other people seem to have a different NullPointerException ticking world crash with different class files:
java.lang.NullPointerException: Exception ticking world
at bwi.a(SourceFile:186)
at bwi.a(SourceFile:92)
at bwm.d(SourceFile:60)
at brt.a(SourceFile:298)
at sj.a(SourceFile:307)
at sk.a(SourceFile:249)
at bbo.a(SourceFile:144)
at sk.i_(SourceFile:199)
at net.minecraft.server.MinecraftServer.w(SourceFile:694)
at net.minecraft.server.MinecraftServer.v(SourceFile:627)
at dii.v(SourceFile:156)
at net.minecraft.server.MinecraftServer.run(SourceFile:532)
at java.lang.Thread.run(Unknown Source)
Mod edit: Copied over from MC-130132:
When loading a 18w20c generated Buffet World (Warm Ocean) in newer snapshot 18w21a, a fatal NullPointerException occurs, causing the game to crash.
To Reproduce
1. Download, extract and place in the saves folder the Minecraft world at http://www.mediafire.com/file/l189qh7bt163aqy/2018-05-23_14-35-40_New_World-.zip/file
2. In the playerdata folder for the save, rename the existing user.dat file to contain your Minecraft UUID (required for issue reproduction)
3. Launch snapshot 18w21a or newer
4. Select Single Player
5. Select the extracted world with your renamed player data file
6. When prompted, click the "I know what I'm doing" button
Notes
Subsequent loads of the world will not generate error, only the first load of the 18w20c will cause the issue
Linked issues
is duplicated by
Attachments
Comments
I just noted my reproduction steps, because I had no clue about why, when, where nor how.
I would like to add how i can consistently cause this error.
i've set my render distance to 2 chunks and generate a new world in 18w21a.
then just move in 1 direction.
if you enable f3 you will see memory usage go up and never drop.
And after a minute or so the game will crash
but i would like to note that my memory was not nearly full yet like 1gb of the 3gb allocated
I don't know if it's helpful, but since my crash report shows different line numbers I will upload it here as well:
---- Minecraft Crash Report ----
// I let you down. Sorry :(
Time: 25.05.18 13:42
Description: Exception ticking world
java.lang.NullPointerException: Exception ticking world
at sl.n_(SourceFile:422)
at sl.i_(SourceFile:220)
at net.minecraft.server.MinecraftServer.w(SourceFile:693)
at net.minecraft.server.MinecraftServer.v(SourceFile:626)
at dii.v(SourceFile:156)
at net.minecraft.server.MinecraftServer.run(SourceFile:531)
at java.lang.Thread.run(Thread.java:745)
A detailed walkthrough of the error, its code path and all known details is as follows:---------------------------------------------------------------------------------------
-- Head --
Thread: Server thread
Stacktrace:
at sl.n_(SourceFile:422)
at sl.i_(SourceFile:220)
-- Affected level --
Details: Level name: #ProjectZelda 1.13
All players: 1 total; [sn['NOPEname'/96, l='#ProjectZelda 1.13', x=10168.79, y=61.24, z=9919.71]]
Chunk stats: ServerChunkCache: 1691 Drop: 0
Level seed: -7581267854039205500
Level generator: ID 01 - flat, ver 0. Features enabled: false
Level generator options: {"flat_world_options":"minecraft:bedrock,30*minecraft:water;1;village"}
Level spawn location: World: (136,31,136), Chunk: (at 8,1,8 in 8,8; contains blocks 128,0,128 to 143,255,143), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 29313699 game time, 5000 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
at net.minecraft.server.MinecraftServer.w(SourceFile:693)
at net.minecraft.server.MinecraftServer.v(SourceFile:626)
at dii.v(SourceFile:156)
at net.minecraft.server.MinecraftServer.run(SourceFile:531)
at java.lang.Thread.run(Thread.java:745)
-- System Details --
Details:
Minecraft Version: 18w21b
Operating System: Windows 8.1 (amd64) version 6.3
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 904723360 bytes (862 MB) / 1677721600 bytes (1600 MB) up to 3221225472 bytes (3072 MB)
JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx3G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=16M
Profiler Position: N/A (disabled)
Player Count: 1 / 8; [sn['NOPEname'/96, l='#ProjectZelda 1.13', x=10168.79, y=61.24, z=9919.71]]
Data Packs: vanilla
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.

@unknown, Thanks. Yes, that's helpful. That way the new obfuscated symbols and line numbers can be found by searching.
This is the duplicate of MC-130088 ?
That was created later, that's actually the duplicate.
Please note that MC-130431 occurred with 18w22a, but my game world did not have a problem with 18w21b, as would be the case with this problem 5 days ago.
Confirmed for 18w22a
[media]I have upgraded my world from 18w21a and it was working fine on 18w21b. However how on 18w22a, it keeps crashing with Exception ticking world. Here is the crash report:
[media]That was MC-130424.

Attached a world where this consistently happens for me, tried in 18w22, 18w21, and 18w16. All resulted in crash
---- Minecraft Crash Report -------- Minecraft Crash Report ----// My bad.
Time: 5/31/18 10:03 AMDescription: Exception ticking world
java.lang.NullPointerException: Exception ticking world at bkm.a(SourceFile:221) at sg.a(SourceFile:312) at sh.a(SourceFile:236) at avg.a(SourceFile:132) at sh.k_(SourceFile:195) at net.minecraft.server.MinecraftServer.w(SourceFile:696) at net.minecraft.server.MinecraftServer.v(SourceFile:629) at dbc.v(SourceFile:156) at net.minecraft.server.MinecraftServer.run(SourceFile:534) at java.lang.Thread.run(Thread.java:745)
A detailed walkthrough of the error, its code path and all known details is as follows:---------------------------------------------------------------------------------------
– Head --Thread: Server threadStacktrace: at bkm.a(SourceFile:221) at sg.a(SourceFile:312) at sh.a(SourceFile:236) at avg.a(SourceFile:132) at sh.k_(SourceFile:195)
– Affected level --Details: Level name: Nier All players: 1 total; [sj['Godlander'/0, l='Nier', x=-989.06, y=104.14, z=963.64]] Chunk stats: ServerChunkCache: 899 Drop: 0 Level seed: -1121374816056803511 Level generator: ID 01 - flat, ver 0. Features enabled: true Level generator options: \{"flat_world_options":"minecraft:air;127;decoration"} Level spawn location: World: (8,4,8), Chunk: (at 8,0,8 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511) Level time: 9823 game time, 9823 day time Level dimension: 0 Level storage version: 0x04ABD - Anvil Level weather: Rain time: 87329 (now: false), thunder time: 63659 (now: false) Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: trueStacktrace: at net.minecraft.server.MinecraftServer.w(SourceFile:696) at net.minecraft.server.MinecraftServer.v(SourceFile:629) at dbc.v(SourceFile:156) at net.minecraft.server.MinecraftServer.run(SourceFile:534) at java.lang.Thread.run(Thread.java:745)
– System Details --Details: Minecraft Version: 18w16a Operating System: Windows 10 (amd64) version 10.0 Java Version: 1.8.0_25, Oracle Corporation Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation Memory: 598721752 bytes (570 MB) / 805306368 bytes (768 MB) up to 2147483648 bytes (2048 MB) JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=16M Profiler Position: N/A (disabled) Player Count: 1 / 8; [sj['Godlander'/0, l='Nier', x=-989.06, y=104.14, z=963.64]] Data Packs: vanilla Type: Integrated Server (map_client.txt) Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.
---- Minecraft Crash Report -------- Minecraft Crash Report ----// Uh... Did I do that?
Time: 5/31/18 10:09 AMDescription: Exception ticking world
java.lang.NullPointerException: Exception ticking world at brp.a(SourceFile:209) at sl.a(SourceFile:299) at sm.a(SourceFile:240) at bbq.a(SourceFile:135) at sm.i_(SourceFile:199) at net.minecraft.server.MinecraftServer.w(SourceFile:693) at net.minecraft.server.MinecraftServer.v(SourceFile:626) at dik.v(SourceFile:156) at net.minecraft.server.MinecraftServer.run(SourceFile:531) at java.lang.Thread.run(Thread.java:745)
A detailed walkthrough of the error, its code path and all known details is as follows:---------------------------------------------------------------------------------------
-- Head --Thread: Server threadStacktrace: at brp.a(SourceFile:209) at sl.a(SourceFile:299) at sm.a(SourceFile:240) at bbq.a(SourceFile:135) at sm.i_(SourceFile:199)
-- Affected level --Details: Level name: Nier All players: 1 total; [so['Godlander'/0, l='Nier', x=-989.06, y=104.14, z=963.64]] Chunk stats: ServerChunkCache: 1062 Drop: 0 Level seed: -1121374816056803511 Level generator: ID 01 - flat, ver 0. Features enabled: true Level generator options: \{"flat_world_options":"minecraft:air;127;decoration"} Level spawn location: World: (8,4,8), Chunk: (at 8,0,8 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511) Level time: 9850 game time, 9850 day time Level dimension: 0 Level storage version: 0x04ABD - Anvil Level weather: Rain time: 87301 (now: false), thunder time: 63631 (now: false) Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: trueStacktrace: at net.minecraft.server.MinecraftServer.w(SourceFile:693) at net.minecraft.server.MinecraftServer.v(SourceFile:626) at dik.v(SourceFile:156) at net.minecraft.server.MinecraftServer.run(SourceFile:531) at java.lang.Thread.run(Thread.java:745)
-- System Details --Details: Minecraft Version: 18w22c Operating System: Windows 10 (amd64) version 10.0 Java Version: 1.8.0_25, Oracle Corporation Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation Memory: 264666984 bytes (252 MB) / 905969664 bytes (864 MB) up to 2147483648 bytes (2048 MB) JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=16M Profiler Position: N/A (disabled) Player Count: 1 / 8; [so['Godlander'/0, l='Nier', x=-989.06, y=104.14, z=963.64]] Data Packs: vanilla Type: Integrated Server (map_client.txt) Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.
We encountered this same crash in a new world generated in 18w22a. I'm fairly certain these are new chunks while we were seeking a stronghold. It doesn't appear the stronghold generated. I can throw my crash report in if it would be helpful.

@unknown, not necessary. there is already a 18w22a crash report attached.
Still happening with 1.13-pre1, we headed off in a direction to look for a treasure from a map. These may be newly generated chunks, same "Exception ticking world" crash. We will try to limp home through the crashes.
EDIT:
As long as we stick to chunks already generated in the Overworld OR explore in the Nether, we are good. This feels like it is an issue with generating new chunks in the overworld, and somewhat random. I also note this crash seemed to break the generation of a Stronghold. Once we generated the overworld chunks looking for the Stronghold, one wasn't there even though Locate suggested one would be and the Enderpearls insisted one was there, except it wasn't. We poked around to find another stronghold much more distant and that one DID generate to the Southwest. We are crashing attempting to go Northeast, and the other crashing seemed to be in that direction. I'm going to see if the server crashes exploring in Spectator traveling in positive only chunks.
...
It seems like I can provoke it in negative chunks, even in Spectator, but it isn't something I can consistently do. It is possible the crashes are tied to chunks partially generated but not completely generated in an older snapshot, but this is just random enough I can't be sure of anything except when it happens, it persists until I push through, teleport out, or out-travel it in Spectator. I know I was generating chunks without triggering this, as I encountered the start of lava falling. Villages were generating also without triggering the crash. Maybe someone else can find some way to reliability cause the crash so it can be resolved. I'd rather not map-wipe again, and I'd really hate to see this in the 1.13 release.
Attached a similar-ish looking crash report (1.13-pre1) happening for me. I had initially thought it was based on some leaf decay stuff (and reported it in another thread) but now it's happening far more arbitrarily, while just mining stone and not even loading new chunks. As reported above, reloading the server and retracing the steps that led to the crash doesn't consistently reproduce it.
Is this still an issue in Minecraft 1.13.1?
I'm not getting this error, but in Spigot 1.13.1 on the Overworld going out some 5k or more from spawn, I'm getting chunks that refuse to load even using F3-A or relogging, I have to reboot the server to get them to finally load in on the client when we reconnect. I'm not clear if that observation is related to this issue or not. I did not report it as I'm not clear if this was a Spigot issue or a Vanilla issue. Hopefully, someone running Vanilla will comment and report if they have the same problem.
FYI Spigot log snip:
This server is running CraftBukkit version git-Spigot-f6a273b-1cf8b5d (MC: 1.13.1) (Implementing API version 1.13.1-R0.1-SNAPSHOT)
INFO Checking version, please wait...
INFO You are 1 version(s) behind
I understand not to report it here if it is, in fact, a Spigot issue. But until I know it isn't Vanilla, I'm not able to report it there either, so I did nothing but note it.

Please check if that's still an issue in the latest 1.14 (pre-)release.
Im experiencing this issue in 1.14 Release although not 100% sure its the same .. crash log @ https://pastebin.com/JSvS9tcC

Yours is another issue
This is not limited to upgraded worlds.
Completely new world in 18w21a. Offline singleplayer, Seed: 18w21a
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