Hi @gduquette
Can you please quickly try with smaller resolution and check if you get the same result.
In case you have Nvidia graphics adapter, please make sure you disable the Nvidia ShadowPlay/In-game overlay/screen recording before connecting the spacedesk viewer.
By the way, which spacedesk Windows Viewer did you use?
Microsoft Store version? Or Windows 7 Viewer (Desktop version 0.9.44)?