I think it's more of a problem with the servers messing up. It happened to me already months ago, with a couple of TV shows. And I have read of the same issue with Grand Tour now using the Apple TV 4K as well. What I did to fix it has been to do a search, then the UHD HDR version appeared. Watching it a bit it moved back to the "COntinue Watching" list (together with the HD SDR version).