Crash while using a lot of pistons/slime blocks (java.lang.IllegalArgumentException: Cannot get property)

Time: 17.11.16 20:10
Description: Ticking block entity

java.lang.IllegalArgumentException: Cannot get property atw{name=facing, clazz=class cv, values=[down, up, north, south, west, east]} as it does not exist in atk{block=minecraft:slime, properties=[]}
	at atk$a.c(SourceFile:166)
	at atd.j(SourceFile:119)
	at atd.f(SourceFile:130)
	at atd.F_(SourceFile:308)
	at ajq.k(SourceFile:1484)
	at beq.t(SourceFile:1649)
	at beq.av(SourceFile:967)
	at beq.a(SourceFile:395)
	at net.minecraft.client.main.Main.main(SourceFile:124)

Crash appears very unreliable when using lots and lots of pistons/slime blocks.