When using a vertical panel with the following layout: - K-Menu (the default one with categories on the left) - Icons-only-Taskbar - Systray - Workspace Switcher - Clock Clicking the Menu button in the upper left quarter activates a program in the systray. The button and the corresponding systray icon have about 650px between them and the icon-only-taskbar. The activated programs are different, I had the problem with tvbrowser (java) and pidigin (gtk), I am not sure if it affects only a certain kind of trayicons. Possibly these programs have trayicons using the older standard. SOFTWARE VERSIONS (available in About System) KDE Plasma Version: 5.13.5 KDE Frameworks Version: 5.50.0 Qt Version: 5.11.1 ADDITIONAL INFORMATION The ubuntu version is 18.10 "cosmic". The problems happened less often in debian buster (currently testing branch), which also has plasma-workspace 5.13.5. I had this problem a long time in earlier ubuntu versions as well, so it may depend on the way KDE is built/packaged.
*** This bug has been marked as a duplicate of bug 357443 ***