There's a bug (no pun intended) when you are playing multiplayer and get the preserved insect relic, if one of your friends joins the elite or boss before you the game doesn't know what HP to put the boss at and will just crash the game. The player with preserved insect needs to join before everyone else for it to work. Got to act 4 with my homie and he joined before me and it cooked the whole run. If anyone knows how to save the run please let me know!