I used 's Pixel to record the issue, but I managed to get some screenshots which show the different issues I've seen. I also captured a burst mode animation whilst capturing one of the screenshots and noticed that the individual photos look fine, but the animation actually shows the wraparound issue I was seeing in the viewfinder UI.
To be clear, the photos taken appear to be fine even while the UI is glitching. The burst mode animation is the only evidence from taken footage. I haven't been able to take a video to see the result.
It didn't happen all the time. I've had this happen while we were out, and a couple of times since we've been home, but at other times the camera works fine.
I'm not sure if this is a hardware issue or an #AndroidNougat camera app bug (my suspicion)