Apple TV 4K 3rd Gen pixelization

We replaced our 2nd gen 4K ATV with the 3rd gen last week. We have a Samsung, so it now provides HDR10+. Mainly it was for Plex, as others have said it improves streaming (I can comfirm this).

We updated our system last year, Samsung Q90T, Marantz AVR, updated HDMI cables, power conditioner, etc ... Connection is via ethernet, directly from AEBS. Our ISP package is 100Mbps, and we get within 99% of that.

The issue with the new ATV is the horrible, and random, blurring/pixelization. At first, it seemed to be mostly with the Apple shows. You could see it right away with the previews they show on top. We were watching Slow Horses, and it was like a lo-rez QT movie from the 90s. I know it sometimes takes a few seconds to buffer, but after letting the show run, it would take upwards of 5 minutes for the proper resolution to snap in.

I know it's a somewhat controversial topic, but I set the new ATV to run in 4K SDR, and have frame rate and dynamic range on. I find this makes River TV (Canada) look better.

The blurring also happens in other apps, namely Netflix. Forcing a restart usually fixes the issue.

I'm at a loss as to what else to try. I've replaced the ethernet cable, tried connecting via wifi, and returning the video settings to 4K HDR doesn't change anything.

We're running 16.3.