Description of issue
All of a sudden the backlog for a specific project doesn't show issues anymore. This started yesterday (Nov 3). I didn't make any changes to the board or workflow settings. I am an administrator, and can see the sprint contents fine, but nothing on the backlog anymore. This issue is happening for all users viewing this project, but other projects are unaffected.
I saw here that another user had the same issue on the same day, but it resolved itself after 24 hours. The issue is still present on my board. I have tried the following fixes without success:
1. Made the filter query as simple as possible (project = "X")
2. Added all unmapped statuses to columns
3. Cleared cache, hard-refresh, tried a different browser
Does anybody have an idea of how I can fix this?
Screenshots
Empty Backlog:

Active sprints view showing tickets:

The settings screens show an error (not sure if this is related):

The columns settings screen:

Getting an http 500 on this board for XHR calls to /data - but not on any other board. Something in one of the issues seems to make the query crash...

Other boards do not have the issue:

Thanks for any/all assistance,
Josh