So far, it happens every time I try to upload an image with drag-and-drop after deleting the current image without saving in between.
I recorded another video using the pencil sketch default image and the site setting interface instead of the config page. But the issue remains the same on both. Though the save button is much further down on the config page, which is why not saving after deleting is more likely there.
Yes, I don’t think the screenshot reveals much more than what I already mentioned in my first post.
It happens with every image I tried.
This is the one used in the recording above.