The last few months I’ve had a problem where the paper in my Martin Yale 1217A paper folder appears to bypass one or both of the bumpers in the folding process. I couldn’t figure out why! Multiple times I took the machine apart, cleaned everything, and put it back together only to have the paper folder jam up on me again. After emailing a Martin Yale tech (they’ve always been super helpful even though I have an older used model), he explained that this sort of problem can be caused by the paper being too hot, too freshly printed. It sounded silly but the next time I had a folding job I let the freshly printed paper sit overnight before the folding process. To my amazement it worked! It totally makes sense to me now, the paper is so much more thin and flexible feeling after being printed that the rollers on the paper folder can’t properly grab. The paper needs to cool to regain some thickness, stiffness and grip.
If you have been beating your head against a brick wall with this issue, try letting your paper cool and see I’d that helps.