In KDE Linux it could happen some issues with windows:
- rules not memorized: to fix it check if configurations files (tipically in ./config/ kwinrc and kwinrulesrc) have the right permissions (avoid: non access).
- new window below others already active: such as Clementine’s window, called from system tray, going below other windows; to fix this you have to set Focus stealing prevention in Window Behavior (the first tab of Window management in System settings) to none, as you can see in the image
.