The color temperature to the right of the rainbow is very different compared to the left of it.
I do use a digital device in my photographic pursuits when necessary.
When someone rags on me for using film, I use a middle digit, upraised.
The Bessa R is a rangefinder; you wouldn't necessarily see the "flare" in the camera's taking lens as viewed through the rangefinder viewfinder.
The camera appears to have been pointing vertically.
Could there have something fallen or laying on the lens?
It almost looks like the edge of a circular filter which has slipped out of place to one side?