We are currently aware of an issue that is affecting Co Op battles, in which when casting a spell that instant-kills enemies can cause the game to error and force restart.
An example is the spell ‘Assassinate’.
Also, I’ve created a Known Issue article for this, so there is no need to submit a ticket.
At this stage, a fix will be coming in v1.2 and the team is working on a temporary fix in the interim.
But once I get any further information I will update this thread.
Jeto (she/they) - Support Human