I'm not understanding whether the tension is loose on the top or the bottom thread? Sometimes when my top thread jumps out of the take up spring (usually cause it gets caught in the bobbin area due to a stray thread or lint) it will create a mess and a loose top tension. Also, are your bobbins getting wound nice and solid, instead of spongy? And have you trimmed off the little tail left when you wind one (from the top hole)? I've been mentoring high school kids making quilts and they have trouble winding those nice solid bobbins and it's caused lots of tension issues.