Modern bobbins vary a lot from the originals. Some like the ones sold by the box stores can run the gamut from OK to flat junk. I've had the best luck buying bobbins from Sew-Classic.
Rather than mess up the machine, make sure the winder shaft is clean of gunk and if nothing else check the holes in the bobbins and enlarge them.
I've got many machines that use the Class 66 metal bobbins and those I've gotten from Sew-Classic have fit all of them.
Basically I'd suggest ordering some from them rather than wasting time "fixing" the others.
~Or~ use another machine they will fit, or one of those Sidewinder type bobbin winders for now.
Joe