Several "specialists" offer so-called redone frames. Usually this means powdercoating only and the most important stuff isn't looked after.
The early 81 frames have a tendency to crack at several places and one which is forgotten can be seen in the picture. I have seen several frames that crack at this area and no one ever looked at it or repaired it, just powdercoat and "it should be ok...". ALthough a repair is only a patch on a tired and stressed frame of that age......