Mobs have been easily forgetting the player and never seem to remember them or where they are whenever they go out of their sight.
Mobs that I encountered so far that has this issue: Zombie, Skeleton, Creeper
Repro steps from comments below:
How to reproduce:
- Go about 40 blocks into the air, and create a little zig-zag walk way out of full blocks. On the corners place glass pillars.
- summon a creeper on one end of the walk way, make it target you, and then walk behind one of the glass pillars.
- You will see the creeper instantly stop, forget about you completely, and just stand there until it decides to randomly pathfind.