I have the same issue on Debian 10.3 with MATE. Strangely enough, I have another laptop with the same setup, and I have never seen it there, I didn't even know this issue exists. Not sure if any of the apps I have installed make the difference (I don't have the above mentioned libremenu installed, i don't even see it in repos).
Btw, there is another duplicate bug #1733078 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1666201 Title: Unexpected behavior in combination with plank and 1 or more panels To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-mate/+bug/1666201/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
