Something like this happened to me a few days ago by pure chance,
It was a black and white Foma 100 film, and I used the process ORWO-4185-e. I took a macro shot of the wristwatch, and the background was a white sheet of paper.
The result is very strange.
The image was positive, but it turned into white and brown and the white background turned into a yellow background.
Unfortunately, I got angry at the failure of the operation, and in a moment of anger I got rid of that negative (positive)
If I had known that this nonsense I did was a good thing I would have kept that negativity