It's over a year that I always have this problem: 1) Use Funtoo Linux "Stable" 64 bits (which is pretty much identical to Gentoo). 2) The problem occurs during the "user change" 3) example: a) within with my user in plasma-5.8.5; Then use "change user" to start the session of the user; Finished the job .... I'm leaving the session of II utesnte. In 90% of cases I get serious graphics errors so much that I have to restart Xorg, thus losing the work of the first user. My system is based on Asus Z97-AR, core i7 "Haswell 4771", 16GB RAM (memtest is ok) SSD 250 GiB + HDD 1 TiB. I'm using Gentoo's nvidia drivers Sandro @ ci74771ht ~ $ emerge -pqv nvidia-drivers [Ebuild R] x11 drivers / nvidia-drivers-378.13-r2 USE = "X acpi driver gtk3 kms (multilib) static-libs tools uvm -compat -pax_kernel -wayland" ABI_X86 = "32 (64) (-x32) I also noticed that there is also a PCBSD with KDE, in PCBSD the "change user" option does not appear in the logout menu. Now i do not know ... and: is a problem with kde? Sddm? Or to nvidia drivers? Or both? Thanks for the attention _'_
Graphics errors indicate a problem in your OpenGL drivers. I suggest to report this to the bug tracker of your distribution. They can decide if the errors are indeed caused by the nvidia OpenGL driver and have to be reported directly to nvidia developers.