Attempt 1: Play Fassie in Solo mode and try to complete the second quest to see if slots will be unlock based on new quest completion trigger. Unfortunally, slot number does not associated with the quest, i.e. slot 2 is not associate with quest 2. Upon completion of quest simply trigger the unlock slot event. So, when finish quest 2, the first slot unlock. I think this is a permanent soft lock. Recommend dev to add a conditional check to match quest progression and unlock status.

while chip_slot.unlocked < quest.completed:

    chip_slot.unlock() 

Also, I saw a quest completion pop up when return to saloon, and the previous quest was completed during a run and then we resume the run later. It is possible that quest is marked as completed, but the unlock event only trigger upon returning to the saloon, and host stop and then continue might cause the event didn't get trigger properly.