PC [BUG] Co-op Skull Key Error

[Ryo_Moon]

There's an Co-op error that happened when I started Co-op on an existing advanced save file: I checked my inventory and Skull Key was not there, then I did go to the 120 floor of the mines but the chest wasn't there so I can't get back the Skull Key.

 

[sailllingaway]

I'm also having this issue. I hosted a co-op game, and now the skull key is missing from my wallet. When I tried to enter the skull caverns it says "The door is locked", and I checked level 120 in the mines for a chest but there's nothing there. So now I can't enter the caverns, and I don't see a way to get another key. Now I can't mine iridium, other gems, and can't complete some quests : (