Originally Posted by CoriAmD
Don't really know what your problem may be, but I have found that when my bobbin starts "misbehaving", it usually means there is a lot of lint build up. Take it all apart and clean the inside of the bobbin casing and see if this helps.
She is right, it may be as simple as cleaning out the bobbin casing. I hope the solution is as simple as that and there is no expense involved because it has to go to the repair shop.