Since Plasma 5.4 (but still occurs in 5.5), frequently when I click anything in the sysem tray, for a few milliseconds there is a "Plasma" window showing in the Plasma panel (no actual window appear on the desktop though). It is too fast for me to capture it with Ksnapshot. It is nothing but it makes the desktop feel "unpolished". :)

Reproducible: Sometimes

Steps to Reproduce:
1. Click anything in the systray or even the clock
2. Try several times if it does not happen the first time
3. Look closely at the taskbar in the plasma panel



Using Dark Breeze theme, Intel graphics