I remember buying a box of Nebs, a heck of deal at the time. Loved it.
Still have tons of it left. Anyway, they wouldn't work to save myself.
Horrible jumping around, snagging, something crazy going on. So, being
the mechanical, anal person that I am, I got out all my test/destruction
tools and started examining the bobbin. What it finally revealed, is
the glue joint where the bobbin halves are glued, and it's not in the
top and bottom as one might expect, the glue joint is in the axis or
circumference of the bobbin itself. There was a small ridge, almost
undetectable. I now use one of the wives emory boards, or a knife
blade, smooth that little bump off the bobbin and they work just fine.
Never had another problem with them. I do about 6 or 8 of them and can
now feel the little bump and take care of it. If you've had trouble
with these, see if that doesn't help. Good luck, good sewing.