Considering changing user and screen locking is broken on XFCE since the switch to 545 drivers,
and possibly KDE Plasma, too,
and that evidence seems to point to the new drivers
see:
Xfce4 black screen with cursor when switching between users
After 2023-12-01 I can not get in to a timed out session
Unable to login on resume due to the “empty” login screen
that a quick search on the web returns a fair number of anomalies occuring on 545
and that 535 is the current recommended production/stable driver here:
https://forums.developer.nvidia.com/t/current-graphics-driver-releases/28500
+1 for downgrading.
or at least have an option to choose between the stable/unstable drivers