Tickets not on the board

We have used YouTrack now on several projects. Suddenly on our current one, it's turned into a nightmare. We find a ticket, set the status to open or in progress and it might appear on the board for a minute, then you refresh and it's gone. I think it's because the guy who entered the tickets nested them quite extensively. Even if that is the case, the way the app handles it is really appalling.

Gonna try to start just unlinking stories as we start work on them.

Any other ideas?

Thanks.