The highlighting bug is a very recent one. I've never seen it before this month. If it's not directly related to the implementation of the vertical tag editor, what would be other recent changes that might possibly be responsible for the bug? And it has to be related to artwork handling on track info panel. My guess is the following two changes:
The side panel reflects the last explicitly clicked track. When you switch tabs the active selected track can change eg. you previously had a file selected in that tab.
The one exception to that rule is the tag editor docked in the main panel, which will change to the current selected track.
Having said that i do see a bug where you click the current selected track in the new tab, and the sidebar panel doesnt update.
To make things more consistent i guess switching tabs should also change the active selected track in the right sidebar
and
i have made a change for the next update based on what i think plausibly may be happening - it would be down to chance so i would need to be working ok for a while to be sure. I also think i know why it wasnt resetting on the next restart. You will still need to manually resave the existing ones with this problem.
Both were right before you implemented tag editor. So maybe it introduced some potential issue, and the tag editor made it active. I hope you review those recent changes you made to see if there's something related to the issue.
One more thing. I don't think whether you can reproduce the bug is such a big deal. It would surely help, but I've seen numerous times you weren't able to reproduce the reported bug for some reason but you managed to fix all those bugs. Maybe this is one of those cases where some users can reproduce more easily than others. I can tell you whether your fix makes any differences regarding this issue even if you can't reproduce it.