Slabs placed on top layer flip to bottom layer

What I expected to happen
I place a stone half slab next to another half slab, both on the top layer. I expect the placed slab to also be on the top layer.

What actually happened
The placed stone slab (every once in a while) flips to the bottom layer.

Steps to reproduce
1. Travel to the end (not sure it is dimension specific, but does happen in End)
2. Build a small platform of half slabs on the top layer
3. Quickly place slabs next to it on the top layer as well. Ever so often, it will flip to the bottom.