Please provide example theme link and *please* in future file those via github. It's difficult or impossible to discuss and fix this here.

If at all possible, please let's continue this on my github issue tracker.

The latest version is able to adapt to themes which should work for nearly every theme. If it fails for one, then this is a bug. Maybe even a Firefox bug that I have to forward to Mozilla.

Edit: Your issue is handled here now:
https://github.com/M-Reimer/undoclosetab/issues/36
Would be great if you could join in and add some AMO links to themes you have problems with.