Hi!
On both of my PC’s I’ve set Firefox to remember tabs that I used the last time, so that I can continue where I left the day before. However, almost every time I boot a Firefox window briefly pops up, and then disappears. Ctrl + Esc shows a Firefox process running, that I have to kill in before I start Firefox in order to bring up my last session.
What could be the problem?
Its intended for a preloaded firefox and faster firefox startup.
You can go to the Startup settings in Systemsettings to disable the preload script to deactivate that behavior.
Aha, I see! But, is it supposed to hide the window? Anyways, I disabled it now, so it should not be a problem anymore. Thanks a lot 
Yeah its the only option to preload firefox in that way. It’s Window is hidden in the ksystraycmd icon in the tray btw.
Oh! Good to know!