Baby chickens don't move when standing on lower slabs beneath solid blocks

There is a weird bug on the behavior of baby chicken:

If baby chicken spawn between a block and a slab, it is expected to walk freely in the 1x3x1 area, just the first picture showed, but they stuck since the pre-release version.

However, if I keep empty or put the slab(bottom) like the third picture, the baby chicken become normal as 1.12.