Old Item frames (from previous versions) in the reserved spawn chunks cause a massive fps drop. 1000+fps down to 3fps.

Removing and or replacing the Item frames fixes the issue.

This error is spammed in the log file:

q: Exception getting block type in world
at ru.f(SourceFile:1206) ~[14w04a.jar:?]
at sc.a(SourceFile:150) ~[14w04a.jar:?]
at arn.a(SourceFile:291) ~[14w04a.jar:?]
at arn.a(SourceFile:81) ~[14w04a.jar:?]
at arn.a(SourceFile:69) ~[14w04a.jar:?]
at nl.f(SourceFile:129) ~[14w04a.jar:?]
at nl.c(SourceFile:80) ~[14w04a.jar:?]
at nl.d(SourceFile:116) ~[14w04a.jar:?]
etc...