In snapshot 17w50a Looping structure block crashes game.

In snapshot 17w50a I have a structure block looping to create an unbreakable structure. It has worked just fine until the new update where activating immediately crashes the game. Has happened in every 1.13 snapshot.

Minecraft Crash Report ----
// I feel sad now 😞

Time: 12/19/17 7:29 PM
Description: Exception while updating neighbours

g: Non [a-z0-9/._-] character in path of location: minecraft:Black Mesa West
at mx.<init>(SourceFile:36)
at mx.<init>(SourceFile:41)
at bai.c(SourceFile:395)
at ayj.a(SourceFile:107)
at ayj.a(SourceFile:95)
at bbi$a.a(SourceFile:419)
at aqy.a(SourceFile:486)
at auf.f(SourceFile:204)
at auf.b(SourceFile:187)
at bbi$a.a(SourceFile:434)
at bck.a(SourceFile:492)
at aqy.a(SourceFile:337)
at auf.b(SourceFile:64)
at bbi$a.a(SourceFile:444)
at qt.a(SourceFile:632)
at qt.d(SourceFile:219)
at net.minecraft.server.MinecraftServer.w(SourceFile:659)
at net.minecraft.server.MinecraftServer.v(SourceFile:592)
at clm.v(SourceFile:152)
at net.minecraft.server.MinecraftServer.run(SourceFile:497)
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 mx.<init>(SourceFile:36)
at mx.<init>(SourceFile:41)
at bai.c(SourceFile:395)
at ayj.a(SourceFile:107)
at ayj.a(SourceFile:95)
at bbi$a.a(SourceFile:419)

– Block being updated –
Details:
Source block type: ID #minecraft:repeater (block.minecraft.repeater // axh)
Block: minecraft:structure_block[mode=load]
Block location: World: (283,57,425), Chunk: (at 11,3,9 in 17,26; contains blocks 272,0,416 to 287,255,431), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Stacktrace:
at aqy.a(SourceFile:486)
at auf.f(SourceFile:204)
at auf.b(SourceFile:187)
at bbi$a.a(SourceFile:434)
at bck.a(SourceFile:492)
at aqy.a(SourceFile:337)
at auf.b(SourceFile:64)
at bbi$a.a(SourceFile:444)

– Block being ticked –
Details:
Block: minecraft:repeater[delay=1,facing=south,locked=false,powered=false]
Block location: World: (283,57,426), Chunk: (at 11,3,10 in 17,26; contains blocks 272,0,416 to 287,255,431), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Stacktrace:
at qt.a(SourceFile:632)
at qt.d(SourceFile:219)

– Affected level –
Details:
Level name: world
All players: 1 total; [qv['Epsi1299'/482, l='world', x=296.88, y=53.00, z=451.93]]
Chunk stats: ServerChunkCache: 4225 Drop: 0
Level seed: -2978931683083982633
Level generator: ID 00 - default, ver 1. Features enabled: true
Level generator options:
Level spawn location: World: (228,60,623), Chunk: (at 4,3,15 in 14,38; contains blocks 224,0,608 to 239,255,623), Region: (0,1; contains chunks 0,32 to 31,63, blocks 0,0,512 to 511,255,1023)
Level time: 14254715 game time, 24347 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: survival (ID 0). Hardcore: false. Cheats: false
Stacktrace:
at net.minecraft.server.MinecraftServer.w(SourceFile:659)
at net.minecraft.server.MinecraftServer.v(SourceFile:592)
at clm.v(SourceFile:152)
at net.minecraft.server.MinecraftServer.run(SourceFile:497)
at java.lang.Thread.run(Thread.java:745)

– System Details –
Details:
Minecraft Version: 17w50a
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: 260005216 bytes (247 MB) / 922746880 bytes (880 MB) up to 1073741824 bytes (1024 MB)
JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=16M
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
Profiler Position: N/A (disabled)
Player Count: 1 / 8; [qv['Epsi1299'/482, l='world', x=296.88, y=53.00, z=451.93]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.