If they cause skipped stitches something is very wrong, not just slightly wrong. My old Bernina will stitch fine with 66 class bobbins, but the stitches isn't that even, particularly zigzag, and it's noisy. Generic bobbins aren't all the same, some might be fine. If they fit perfectly in the case, and turn as they should, I dont see why you shouldn't give them a chance? I aim for the right kind of bobbin, and anything else is when I'm forced to take a chance.