The 15 x 1 needles will hit the bobbin case and nick it over time. The 15 x 1 needles are longer and not made for this machine. Proof of this is that all of the 319's I've ever seen have had original bobbin cases that look partially chewed on. So, not a good idea;> Nancy, is it possible the hook assembly was knocked during travel and or being put into the table? Maybe a good knock did something to the timing. I've never touched the "bite" of the 319 and have had no stitchout problems. If the heavier needle doesn't help, then the other option would be to tweak the hook assembly a bit.