I'm having this issue too but worse since patch 3 on PC in Act 1 Underground it has completely broken my game.
All the game menu's are laggy, sometimes icons don't show up, every action is delayed, the walking animation for each character stops working entirely, Map doesn't load, sound and music flickers on and off, textures load slowly or barely load, everything is broken.
No changes to the settings fixes it or different saves.
I have a very powerful PC which could run everything on ultra without any lag prior to this patch.
