Merge widget goes to endless "Checking ability to merge automatically" loading spinner when tab has been stale for a while
NOTE: This issue is currently blocked by &5598 which seeks to improve mergeability checks making it easier to diagnose and remedy these issues.
Summary
When I leave a merge request open that had all content loaded and come back to it after a while, quite often the merge widget goes back to Checking ability to merge automatically again with a loading spinner, but never progresses to the next state. I was able to record one instance of this and also recorded the console output and network tab in case there might be something interesting going on there.
This has now happened at least 2-3 times per day over the last week for me. My browser is Firefox 78.0.2.
Steps to reproduce
I haven't figured out what exactly is triggering it, but it's been happening both for the gitlab-org/gitlab project as well as the gitlab-com/www-gitlab-com project. Usually it happens when I leave a tab open, work a while on other tabs and then come back to it. On a recent merge request, it also showed up after I switched between "Changes" and "Overview".
Example Project
The most recent MR where I was able to reproduce it on a couple of times was gitlab-com/www-gitlab-com!55392 (merged).