Even with a reboot from the system menu, I can’t get it to stop for long. I’m starting to suspect it is tied to watching something in 4K then going back to a non-4K source where it happens. I watched a Netflix 4K video and came back and lo and behold it was motion smoothing city on my Xfinity box content. Happened earlier in the day when I switched to AppleTV to watch HBO Max and came back. I wonder if that might be a connection?