Add an emote that a player can use when they are stuck in combat to fix it.
The emote will make it so that the player will dance around wildly playing a musical instrument for around 10 seconds, increase the damage they take for the duration by 1000x , prevent them from being able to be healed, shielded or linked to another player, prevent them from being in stealth, and prevent them from terminating the emote early.
If the person isn't dead by the end of the 10 seconds it's probably safe for the game to assume it would not be excessively disruptive to mark them as not being in combat.