I'm starting to see a trend here on these 4K HDR HDCP de-sync issues.
It looks like most sets that are affected tend to be from Samsung. Anything from the JU7100 series (what I've got) all the way up to the present day. It's not entirely Samsung sets experiencing this problem, but seems to be heavily weighted that way.
Doesn't seem to matter whether people are feeding through a receiver or not, but we all tend to experience "Everything's fine, I can view 4k HDR content without a problem!" followed up minutes, hours, or days later by purple screens, HDCP errors, distorted colors, etc.