System tray icons won't pop out

My KDE system tray icons is quite standard (time, network connection, sound, etc). Usually, clicking on one of those icons makes a pop-up appears, and allows e.g. to select the media to mount, to change the volume, etc. Something like this: However, sometimes (I'm not sure what triggers it), clicking on an icon does not have any effect (beside adding a blue bar on top of it): I feel like this happen particularly when I'm transferring large files, and the "on going task" icon is active for a long time, but could be wrong. $ plasmashell --version plasmashell 5.8.6 $ kf5-config --version Qt: 5.7.1 KDE Frameworks: 5.28.0 kf5-config: 1.0