xfce4-panel shows a pile of overlapping pop-ups "unexpectedly left the panel" every other time I log in to X

Hi! 👋

I'm a happy user of XFCE, thanks for making XFCE and sharing it as Open Source! 🙏

When I log into X about every second time, xfce4-panel shows a pile of overlapping pop-ups saying "Plugin [..] unexpectedly left the panel" — screenshot below — that force me to either

• click "Execute" multiple times or
• do "pkill -9 xfce4-panel && xfce4-panel &" on a terminal.

If that could be solved, that would be fantastic.

For potential causes I can think of:

• use of some de-facto dependency before its available,
• use of a non-monotonic clock and NTP/clock updates hitting at the same time, and/or
• some other race condition.

Thanks and best

Sebastian

PS: This is ticket https://bugs.gentoo.org/810850 in Gentoo Linux if of interest.