Something else to check about the bobbin. A friend of mine had a Brother embroidery machine and a Brother Sewing Machine and the bobbins were very slightly different. They both fit both machines and sometimes they worked fine but sometimes they caused problems, and her life got a lot better when she simply threw away all her bobbins and started out with new ones, marking the sewing ones with a permanent marker.
So if something like that is possible, start with a fresh known to be correct bobbin. Double check your package if you still have it to confirm you have the correct one.