We've got a series of events listed, similar but not identical (separate instances of each), and on a few occasions, the tickets for an event are simply gone. We've added them successfully in the past, even in one case had a few registrations already successful. Then we open the event some time later, and the remaining tickets are gone and we have to add new tickets again.

*These are paid tickets.

Are we doing something to delete them without realizing it? Is this somehow happening when we clone an event to create another iteration of it? Or is there a bug?