I was going to say. You don't have to treat these as black boxes. You can even look at the raw magnetic signal and see exactly how it's out of spec
We also had special head alignment tapes that would be used just prior to an important recording. Usually this was a single screw, one side of the head would be held fixed in place and the other could be adjusted up or down against a spring, the head would tilt relative to the tape running direction. On very fancy multi track recorders you could also lift the whole head up and down so the (very small) heads would match up with the tracks.