Just ran into a similar problem. It happened on three tapes for a recital. One day shoot unfortunately. But it wasn’t from dirty heads. I wound and rewound the tapes beforehand with a DV deck that was giving me trouble (ejecting and shutting down). I am not sure if that scratched the tapes, but that in fact is exactly what happened. The first 12-20 minutes of each of three tapes were scratched at an angle across the surface. I manually turned the tapes and saw it. Cut right across the tape surface in random spots for the first 12-20 minutes.
I doubt that the tapes came that way, although I haven’t completely ruled that out.
John