TxKreator

still in 18w11a

on windows 7
with 18w10d when you make a new symlink (delete the old) with /d /j option it work
(without /j it crash)

still in 18w10d

can confirm on windows 7
with 18w10d when you make a new symlink (delete the old) with /d /j option it work
(without /j it crash)

still in 18w10a

Still in 18w10a

still in 18w09a

Confirmed present in 18w09a

sad because i changed so much in my world, the backup is far away from now

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)