Debian 9.2
64-bit
KDE
KDM login manager

My wife and I share this desktop and if I lock my screen and later she wants to use it, she moves the mouse to wake up the screen and it shows my account locked, but the switch user option is gone and she cant login without me logging in first and then selecting switch user or me logging off. I think (not sure though) this started happening when I updated to Debian 9.2 from 9.1 because it was working fine before.

Any ideas? let me know if you need me to post contents of any related files.

Thank you
Erik

Seems to be fixed now, though without any intention on my part, other than a simple reboot. Go figure.

No, I have no any idea, but I think the GUI (the X server, or some part of it) is not stable enough, so if you used a lot of resources strange things may happen - like this.