Feed down?, Quilt tension tight, but not too tight? Quilt less than a finger from the bed of the machine (too high and it causes issues, too low and it drags on the machine bed)... What speed are you running your machine, could it be too slow and your moving the machine at the time it's in a needle down causing it to pull against the fabric... I'm just trying to think of different things..
Let us know how its going..