Hmmm maybe it is the spray basting. Maybe it was too thick. I think I had that with one quilt. You can still spray baste but lightly. I agree with others rethread. Is the thread strong enough? Is the bobbin thread the same or slightly thinner? You can also try and free motion with the feed dogs up. Are you using a top stitch needle with a large eye and a little bump on it to open up the fabric like a Schmetz 90/14 topstitch needle? Do you have the machine set to quilting mode, if that is an option? Often you need to loosen the tension a couple of settings.