Certainly the gain pot getting dirty is also a potential issue, though that never happened with my DAT deck.
The wheel moving is a real issue on the M10 also because, unlike on a DAT where the gain knob was on the top of the unit, in the same place as the line-in, on the M10, it's on the side. So if it's in your pocket and you pull it out, it's more likely to rub against your clothing or your hand and move. I don't recall if I ever tried to put my D8 in my pocket, as I'd have needed a pretty big pocket, but that design would have, in theory, made it less likely to have that happen.