I had this same problem, it may not be the bobbin though. We thought it was nd tried evrything to fix the darn thing! Finally we figure out it was the thread kept popping out of the take up lever. As soon as it would make that noise like it was hesitatng, i would check and sure enough, it had popped out again! It hasn't much since, but at least i know how to fix it and it's quick and easy to do.

Sounds like your bobbin wasn't wound tight enough. Try winding another bobbin and see if that helps