[MC-142661] itementity falls throug blocks abpve y=64

An Itementity thrown on a block above y=64 will fall throug all blocks (tested with concreteblocks) and land on the firstblock below y=64.

Environment

Windows 10 pro, Java 8 181

Is this on a superflat world? If so, does MC-141100 describe your issue?

Yes, well kind of it's in a superflat but it is not just somtimes but allways. and also a different y-Level so I guss ist different.