SUMMARY When desktop workspace is switched while a tray popup is visible, the tray popups become unresponsive and can no longer be displayed. STEPS TO REPRODUCE 1. Open a try popup by clicking on any tray icon 2. Switch desktops e.b. by mousewheel while the mouse pointer is at some free space 3. Try op open and close tray icons, it does no longer work OBSERVED RESULT Tray icons are unresponsive after switching desktops while a popup is displayed EXPECTED RESULT Tray icons work as before SOFTWARE VERSIONS (available in About System) KDE Plasma Version: 5.12.5 KDE Frameworks Version: 5.45.0 Qt Version: 5.9.4 ADDITIONAL INFORMATION Bug was described in the forum at https://forum.kde.org/viewtopic.php?f=67&t=150659&p=393747
Just found bug 384220, which also describes this problem. So I mark this as a duplicate.
*** This bug has been marked as a duplicate of bug 384220 ***