Apologies for the late reply, I was gone all day.
It's a tad hard to describe what it looks like, but it is completely static apart from the edges, which are... flowing? They have this wavy quality to them, if that makes any sense? I kept an eye on the UI and nothing seemed to change, the only idea I have is that it may be something with the light meter?
The thing that really messes with my head is that I cannot fathom what it's tied to - I thought it was lighting, but the oval appears and disappears when I leave the camera idling and step away from my PC, so it's probably not entirely that either?
It is for sure some kind of overlay, as it is affected by the cat's eye (When I press Z, the reticle stays white but the oval turns into a light shade of gray), so maybe it is something with Godot itself? It could be anything, which is the fascinating part.
I'm really not sure what this is caused by, but I hope that it may fix itself with a new version. If push comes to shove I'll just download it on my laptop instead, but it'd be a shame to not experience this game as it was meant to be played.