Probably some compatibility problem with top-icons-plus?
Sometime the menu shows up, sometimes it doesn't. The code we trigger is 100% the same every time:
self.tray_menu.popup(None, None, None, button, time)
Yet the result varies.
Since GTK2 is going to be dropped soon, I'm not going to fix this. Just a warning that as we well know, system tray support on Linux is a complete nightmare.
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/2392