Hey,
I realise its a pain but I've not given up on this. All I can suggest is you upload everything to the FTP so hopefully I can duplicate the issue. I know is a pain but until I can duplicate issues here we are out of luck. I don't have any 4k displays on the cab, all I can do is test 4k content. That all seems to work without issue.
I do have a separate machine with a 4k display and that's been running in the screensaver for days without issue.