I’m not sure if this is a bug or not but here it goes.
This happened to me too. It’s when you land on the enemy boss and stand on his “head”. You still can get him by autoattack but most skills don’t work.
This is not a lag. This is a placement bug. The boss is just below your caracter.
Bug
This is something I have noticed in the level 30 Mushicara boss fight. He likes to glitch and move around and when he jumps up you cant seem to dodge it wherever you are on the map. Most likely it is because of the move glitch so he seems like he is farther away but, actually right next to you.