Enemies unable to be hit Reference# 2,853,217,409

I've been noticing a weird issue where my build causes the games frames to tank from 100+ down to sub 30fps and when it does normal mobs (not all of them) tend to just break. They'll do walking animations, some will even follow you like a pet but theyre unable to be interacted with. I cant kill them, they cant hit me, theyre just there.
Additionally there have been even fewer instances where the mobs will follow, unable to be damaged (not evade enemies or proximal tangibility. I checked) and after about 30s they will randomly turn into actual aggroing enemies and hit me from behind. Again, this only seemed to start happening when my spell effects go off in a chain explosion and the fps tanks.