zerdguyyy

Thanks Neko! That would make sense. 🙂
Here's the crash report.

Minecraft Crash Report ----
// Why did you do that?

Time: 6/11/17 4:10 PM
Description: Ticking block entity

java.lang.IllegalArgumentException
at rq.a(SourceFile:18)
at rq.a(SourceFile:37)
at ami.i(SourceFile:141)
at ami.c(SourceFile:128)
at avw.e(SourceFile:91)
at ams.k(SourceFile:1417)
at om.k(SourceFile:547)
at net.minecraft.server.MinecraftServer.D(SourceFile:632)
at net.minecraft.server.MinecraftServer.C(SourceFile:560)
at chb.C(SourceFile:154)
at net.minecraft.server.MinecraftServer.run(SourceFile:464)
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 rq.a(SourceFile:18)
at rq.a(SourceFile:37)
at ami.i(SourceFile:141)
at ami.c(SourceFile:128)
at avw.e(SourceFile:91)

– Block entity being ticked –
Details:
Name: minecraft:mob_spawner // avw
Block type: ID #52 (tile.mobSpawner // arx)
Block data value: 0 / 0x0 / 0b0000
Block location: World: (186,73,245), Chunk: (at 10,4,5 in 11,15; contains blocks 176,0,240 to 191,255,255), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Actual block type: ID #52 (tile.mobSpawner // arx)
Actual block data value: 0 / 0x0 / 0b0000
Stacktrace:
at ams.k(SourceFile:1417)
at om.k(SourceFile:547)

– Affected level –
Details:
Level name: bug?
All players: 1 total; [oo['Zerdguyyy'/558, l='bug?', x=187.24, y=74.53, z=243.57]]
Chunk stats: ServerChunkCache: 272 Drop: 0
Level seed: -1558627067970984661
Level generator: ID 00 - default, ver 1. Features enabled: true
Level generator options:
Level spawn location: World: (176,64,248), Chunk: (at 0,4,8 in 11,15; contains blocks 176,0,240 to 191,255,255), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 967 game time, 967 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 145624 (now: false), thunder time: 109290 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
at net.minecraft.server.MinecraftServer.D(SourceFile:632)
at net.minecraft.server.MinecraftServer.C(SourceFile:560)
at chb.C(SourceFile:154)
at net.minecraft.server.MinecraftServer.run(SourceFile:464)
at java.lang.Thread.run(Thread.java:745)

– System Details –
Details:
Minecraft Version: 1.12
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: 170916360 bytes (162 MB) / 472649728 bytes (450 MB) up to 1060372480 bytes (1011 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 6, tcache: 0, allocated: 13, tallocated: 95
Profiler Position: N/A (disabled)
Player Count: 1 / 8; [oo['Zerdguyyy'/558, l='bug?', x=187.24, y=74.53, z=243.57]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.