I’ve just switched to Windows and have started getting this problem. Black images uploaded as screenshots and often I get images of the pairing screen uploaded too.
I was previously using an ipad, with an android (Samsung s10+) companion app and screenshots would load normally - either automatic or snapshots I took myself.
The current set up is a Windows 10 business level laptop connected to a TV via HDMI and runs full screen on both laptop and TV. Works beautifully, except for this issue.