when wierd things like that happen to me, it almost always turns out that i have either the top or bottom threaded wrong. (it's true. after all these years, i still get it wrong sometimes. go figure.)
from the looks of things, the problem seems to be somehow related to the bobbin.
have you taken out the bobbin case recently to clean under and around it? if not, maybe you should. if you have, maybe it isn't seated exactly right since you put it back in.
are you sure the foot is properly attached? feed dogs all the way up? foot pressure on a moderate setting?
before you wreck your quilt, make a test sandwich of fabrics and batting to work on while you figure it out.
i'd take it in to the dealer. let him put it through its paces. if it isn't defective, he should at least be able to help you figure out what's causing the problem.