I have a 120 back for an RB67. This one has a winding problem too, but it's easily dealt with by pressing on a certain spot when closing it, to be sure a tiny lever behind the edge is engaged. Once I figured this out, it has never failed me. I'd like to sell it with the body, which has no front cap, or with the body and 90mm lens, which also has no caps. (They were burgled from me some time back, and recovered this way.) If you'd like them in spite of these glitches, make me an offer; I'm not likely to refuse anything reasonable.