On Jun 22, 2020, at 2:39 AM, Jim Stutsman via groups.io <onlinesewing@...> wrote:

BEFORE YOU TAKE IT IN - Remove the needle plate and bobbin holder. Use magnification and a bright light to closely inspect the rim of the silver "basket" that the bobbin case rides. In 25 years of servicing machines every time I was presented with a machine that "eats bobbin cases" there was damage to the hook race. Small pits usually just cause clicking while sewing, but nicks and deep gouges will cause the stitch to catch and not release properly. That will pull the case up and spin it, causing this kind of problem and usually more damage. Many dealers never look for this. There is a tool available to them (Part #OILSTONE) that will polish out minor damage, but if the hook race is notched or deeply damaged it should be replaced.

Another thing to check is the position of the bobbin case and stopper. Look at the area circled in this photo. The little "nub" on the bobbin case should be in full contact with the stopper. If the stopper is too far toward the front of the machine it is super easy for the case to pop up and spin, especially at high speed. Also note the position of the spring that the case bumps up agains. It should be absolutely straight as shown in the photo. If it is bent, or worse, missing, the stopper should be replaced.

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