I found an issue where a zombie, a husk, or possibly other mobs as well couldn't find a way to get to me, when all it needed to do was jump up a block.

The husk doesn't know how to get to me in this picture.

How to reproduce:

1. The middle block behind the husk is a full block,

2. Wrapped by a 3x3 ring of slabs,

3. Then the outer layer (5x5) is one block with a slab on top of it, 1.5 blocks high.

4. Spawn a husk anywhere inside and it can't get out.

This also happens with zombies, and most likely with drowned and zombie villagers as well.