Is the main monitor instantly frozen when the spacedesk connection is made?
For further analysis, could you please send us the diagnostic logs on your primary machine.
Just run spacedesk Driver Console -> Diagnostics -> Save All Information.
PS: Saving all information will take a few seconds, then please send us the whole folder which contains all the diagnostic logs collected.
Please right-click the folder -> Send to -> Compressed (zipped) folder, then attach the *.zip file in your next reply.
Thank you very much for sending the diagnostic logs.
It seems that Nvidia ShadowPlay/In-game overlay is currently running on your primary machine. This Nvidia feature is incompatible with spacedesk, you can verify it on spacedesk Driver Console -> Diagnostics -> Incompatible Software/Product.
Please make sure to turn off this feature before spacedesk connection.