Currently otherwise identical monsters (goblins in the vaults, summoned creatures, even normal monsters in levels) - frequently switch places between each other, even if you attack them.

The goblin misses you. The hobgoblin misses you. The hobgoblin squeezes past
the hobgoblin.
You check your surroundings. The goblin misses you.
You check your surroundings. The female hobgoblin squeezes past the hobgoblin.
You check your surroundings. The goblin misses you. The female hobgoblin
misses you.
You check your surroundings. The goblin misses you. You block the female
hobgoblin.
You check your surroundings.
You check your surroundings. The female hobgoblin misses you. The goblin
misses you.
You check your surroundings. The female hobgoblin misses you. The goblin
misses you.
You check your surroundings. The female hobgoblin misses you.
You check your surroundings. The goblin misses you. The hobgoblin squeezes
past the female hobgoblin.

This really messes up pickpocketing because you need to tediously keep track if you are already pickpocketed this monster, or not, and pickpocketed monster already squeezed his way out.

Making only panicked/blind raged/stronger (summoner can squeeze past his summons) monsters able to squeeze past the others will be really great quality of life improvement for Pick Pockets.