I noticed that all the pictures I have taken the other day have the top right corner that is black (see example below). There is various pictures with different aperture and exposure, all with the same problem but more or less marked but it doesn't look like it depends on the aperture nor exposure.
I have read the answers to this question, but it doesn't cover my problem.
The picture were taken with a sony a7iii with the sony FE 1.8/50mm lens, without any lens hood. I tried to reproduce the problem back home when I noticed it (the camera was still in the same setup) but couldn't.
What causes this black top right corner? Could cold cause this? Is there a defect on the shutter?