David,

What SM version are you running? Is it 64bit buster based? If yes, what window manager are you running?
Have you seen the 'mutter' discussion?
indilib.org/forum/stellarmate/11148-high...ter-sm1-7.html#81754

And Alacant's hint on noxdamage switch could help with the server side.
On the viewer side, there is an 'options' dropdown where you can set various connection options that may also help.


Gene

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