Unsure if this is specifically related to FPS lowering to ~20 or actual movepseed buffs while also having over 50 acolyte minions alive. Player and sometimes monsters simply run in place when attempting to move. In the user’s case, the player character often can’t change direction if they were already moving when this happens. The player can cast and teleport normally while this is happening, and the issue usually only lasts for ~2-4 seconds at a time. MOST enemies and minions on screen continue to move as normal while this occurs.
I first encountered this on an acolyte (around 60 wraiths + 6 skeletons up at all times) around wave 700 arena when too many enemies would spawn – larger groups like spiders caused this issue every time they spawned and ran towards me.
My wraiths were spec’d into movespeed if casted from corpse.
After using a similar spec but also using two golems that have max movespeed buff, the issue also occurs sometimes in the monolith. I also saw a few void enemies running in place while it was affecting my character, but most minions and enemies continued moving as normal.