For further analysis, could you please run the spacedesk Driver Console app on your primary machine, then click Diagnostics -> Save All Information button, then send us the diagnostic logs.
Just right-click the folder -> Send to -> Compressed (zipped) folder, then attach the *.zip file on your next reply.
Can you also please tell us your secondary machine info:
– Operating system
– spacedesk Viewer app type (Android/iOS/Windows7/Windows10/HTML5)?
– Network type (wired/wireless)?