OK, so I finally killed that form.
One, that needs to be deleted, is not 8915F-T. That's the one that shows error message next to it in the forms view.
One that, actually has to be deleted is one above it - 8915T, and it does not have red ! next to it. Apparently, 8915T contains erroneous 8915F-T in it and, simply deleteing that subfoirm, produces no result.
So delete 8915 T. My return was just transferred, as it should.
