Hmm. Can you ssh to the machine and try to capture a screen from the console? (assuming it won't redraw full screen before taking a grab).
Or, alternatively, if you're willling and have time - you could perhaps try `monitorsim` from
https://github.com/mlukaszek/evdipp/. Firstly, it would show if similar corruption can be reproduced with any evdi client, but also - this makes screenshots every 10s and saves it to a PNG file.
Cheers,
Michal