Thanks for your reply. I just connected from the LINUX PC to the WIN11 PC and it appears that connection is fine. These are on the same LAN (one wired and one wireless).
I will try the WIN10 to WIN11 connection again when I go back to the WIN10 location this weekend. I will try disabling hardware decoding and will try to gather logs from the two computers. I may try using a LINUX laptop to connect to the WIN11 PC, through the WIN10 PC. I would expect to have similar issues.
What really seems strange is that this exact connection used to work well. I spent many hours sitting at the WIN10 PC while connected to the WIN11 PC (up to about 2 months ago+/-). I do not know enough about NoMachine to have made any settings changes (knowingly). I always suspect Windows upgrades for causing strange problems.