[MC-126401] Game crash when exploring upgraded 1.12.2 world

I was just swimming around an old part of the SMB server and the game crashed with the error below. Reloading the world crashes straight away.

[Server thread/ERROR]: Encountered an unexpected exception
h: Exception ticking world
at net.minecraft.server.MinecraftServer.w(SourceFile:698) ~[18w08b.jar:?]
at net.minecraft.server.MinecraftServer.v(SourceFile:627) ~[18w08b.jar:?]
at cxd.v(SourceFile:155) ~[18w08b.jar:?]
at net.minecraft.server.MinecraftServer.run(SourceFile:532) [18w08b.jar:?]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_74]
Caused by: i: Non [a-z0-9/._-] character in path of location: minecraft:CaveSpider
at nx.<init>(SourceFile:36) ~[18w08b.jar:?]
at nx.<init>(SourceFile:41) ~[18w08b.jar:?]
at atj.g(SourceFile:42) ~[18w08b.jar:?]
at atj.b(SourceFile:185) ~[18w08b.jar:?]
at bfe.a(SourceFile:86) ~[18w08b.jar:?]
at bfe.ac_(SourceFile:104) ~[18w08b.jar:?]
at jp.<init>(SourceFile:53) ~[18w08b.jar:?]
at sd.b(SourceFile:105) ~[18w08b.jar:?]
at se.c(SourceFile:145) ~[18w08b.jar:?]
at rx.k_(SourceFile:219) ~[18w08b.jar:?]
at net.minecraft.server.MinecraftServer.w(SourceFile:694) ~[18w08b.jar:?]
... 4 more

Linked issues

duplicates 1

MC-124123 Crash upon loading world: Non [a-z0-9/._-] character in path of location: minecraft:Zombie Resolved

Comments 1

TxKreator 2018-02-26T13:49:40Z

Same problem here (but Skeleton not Spider [and on Windows 7/10]):

Map from 1.12 to Snap 18w0Xx and in one Chunk it crash.

when you play the map on a server the whole server crash

Description: Exception ticking world

i: Non [a-z0-9/._-] character in path of location: minecraft:Skeleton
	at nx.<init>(SourceFile:36)
	at nx.<init>(SourceFile:41)
	at atj.g(SourceFile:42)
	at atj.b(SourceFile:185)
	at bfe.a(SourceFile:86)
	at bfe.ac_(SourceFile:104)
	at jp.<init>(SourceFile:53)
	at sd.b(SourceFile:105)
	at se.c(SourceFile:161)
	at rx.k_(SourceFile:219)
	at net.minecraft.server.MinecraftServer.w(SourceFile:694)
	at net.minecraft.server.MinecraftServer.v(SourceFile:627)
	at cxd.v(SourceFile:155)
	at net.minecraft.server.MinecraftServer.run(SourceFile:532)
	at java.lang.Thread.run(Unknown Source)