I know there are better ways to do this, but we have a "bug triage" sprint that we use as a bucket for all new defects. As QA/testing finds things, they assign them to this sprint. As defects are triaged, they have necessary fields populated, etc., and are then placed/prioritized in the backlog.
This sprint has been "emptied" of issues many times (that's the target state, after all). For some reason, though, now when it's emptied, it no longer shows on the board. If I create a new issue, assign it to that sprint, and refresh the board, the sprint appears and shows that one issue. If I delete that issue or assign that issue a different sprint and refresh the board, the sprint disappears again. Any idea what might be happening here?