Have several B&J cameras, they have performed very well over the years.
I have not found anything on the Big B&J that could not be fixed. It could be as simple as a missing C clip that allows the geared shaft to shift back and forth. Look at it closely and see if you can find why it is doing what it is doing. If the wood and Bellow is ok I personally would try to fix it. If you paid a bunch for it, and feel it is just a "beater" (more than $300.00) you just might be ahead to ship it back and hope for a better one to come along..
I have two 8X10's that I woulden't sell for a thousand dollars. I actually like them that well.
Charlie.......................