When struggling with a persistent issue like this in FF devtools it can still be worth filing an issue on the bugzilla tracker. Worst case, it gets closed as not reproducible. In practice many of these issues will eventually get caught if enough people complain about them and someone manages to dig through all the reports and come up with theories about the issue.
You may get a helpful reply from someone on the team with suggestions on how to troubleshoot it, like enabling specific logging flags or pulling some info out of the console.
I've filed lots of bug reports against Firefox in the past and just because you don't have an isolated reproduction case for a devtools issue, that doesn't mean it can't be fixed.
