Failed to save chunk java.io.UTFDataFormatException: encoded string too long: 65541 bytes

I can relate to this one but it doesn't freeze for me just a massive fps drop, I've tested a few things up and it looks like it does this when I use the /kill and I get to the spawn chunks, my fps goes from stable 120fps to 18-20fps max, if I go around 20 blocks from the spawn point, everything is back to 120fps, if I wait around 1 minute and go back to spawn, fps is stable again too but if I'm too quick, fps goes down to 19-20fps at the exact spawn location.

Ok, it is very weird, I happen to have the ender dragon egg placed at my spawn, and the problem goes away when I disable Entity Shadows. Enabling Entity Shadows make it drop fps and freeze.

I started to get this on the logs:

[10:11:25] [File IO Thread/ERROR]: Failed to save chunk
java.io.UTFDataFormatException: encoded string too long: 65541 bytes
at java.io.DataOutputStream.writeUTF(Unknown Source) ~[?:1.8.0_51]
at java.io.DataOutputStream.writeUTF(Unknown Source) ~[?:1.8.0_51]
at ea.a(SourceFile:29) ~[15w31a.jar:?]
at dn.a(SourceFile:407) ~[15w31a.jar:?]
at dn.a(SourceFile:54) ~[15w31a.jar:?]
at du.a(SourceFile:45) ~[15w31a.jar:?]
at dn.a(SourceFile:407) ~[15w31a.jar:?]
at dn.a(SourceFile:54) ~[15w31a.jar:?]
at dn.a(SourceFile:407) ~[15w31a.jar:?]
at dn.a(SourceFile:54) ~[15w31a.jar:?]
at dx.a(SourceFile:91) ~[15w31a.jar:?]
at dx.a(SourceFile:79) ~[15w31a.jar:?]
at aov.b(SourceFile:139) ~[15w31a.jar:?]
at aov.c(SourceFile:124) [15w31a.jar:?]
at awb.c(SourceFile:37) [15w31a.jar:?]
at awb.run(SourceFile:30) [15w31a.jar:?]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_51]

That's why I tweeted the warning about using books or signs in this snapshot.

Im getting similar feedback

3:57:45 PM CONSOLE: IO Thread/ERROR]: Failed to save chunk
3:57:45 PM CONSOLE: string too long: 65543 bytes

We've had Books and Signs auto cleared from the start so were never used.

note, if you really want to save that world, but don't have any backups and you didn't do much with new 1.9 stuff, you can open the world in 1.8 and quickly save it to downgrade its version, then open that world in mcedit and remove every sign/book manually.