Its an enrage issue. Alchemist tends to run a little space in the opposite direction hes facing whenever he enrages. However if his back is close to a wall when he enrages, he tends to try to run to the otherwise of the wall then and it can cause him to run to areas that force him to reset.
This issue is heightened with the collision issues you implemented in this version. Enemies will try and run away if they're colliding with any object, and can cause them to run into reset areas if you're fighting near their reset border (which happens commonly at alchemist due to the pathing bug near the bottom left of his area).
The collision issue also causes enemies to sometimes just run in circles and constantly trying to find an acceptable area in which they're not actually colliding with anything. We've actually gotten Brood Matriarch to completely glitch out by heavens edging and getting her stuck on a tree + the berserker, and she just stood there doing nothing while we killed her. The collision issue I think also causes the enemies being invulnerable. If they're chasing you, and then you get outside of their "Reset area" but then get stuck on something while trying to return to their original position, they'll sit there being stuck until they're told to teleport back to the original spawn location, but I believe they'll stay invulnerable instead of returning to an attackable form.