My 4K+ is set to use the “Black” screensaver; wait time is 1 minute; “Use dim if paused during video playback” is not checked.
Since the October release, it seems like the screensaver has stopped working entirely.
Are you using the Suspend option? If so – it’s probably a duplicate of Screensaver not working after resuming from Standby. Interestingly this seems to have been introduced some time ago; but only discovered recently.
I’m on it.
Cheers
Sam