> Are these rootless sessions?
Yes.
(TBC, I connect by asking for an xterm if one is not running already. It then behaves like it was a local window, including that I can move it between local monitors, except it corrupts other windows that overlap it. I do not get a copy of a physical screen that would show one remote monitor at a time but allow me to switch between them.)
> We aren’t aware of similar issues and it would need a thorough investigation,
I suppose that is good news, though it is also surprising given that the screen corruption is immediately reproducible with multiple display drivers and implementations of X, and then on a distribution known for its stability.
> something that is probably best done through the traditional support channel. It would be wise to update to a more recent version of NoMachine 8 first, if updating to version 9 is not possible, and see if that helps.
Many thanks. I’ll ask our IT to try both.