We use this same machine at work. 1. Do you have the bobbin in the case correctly? Bobbin should unwind clockwise. 2. Do you have the bobbin thread completely seated under the tension spring? 3. When you put the bobbin back into the machine, do not have the little flip handle out. When you press in the bobbin case you should hear/feel a click. 4. When you thread the machine, you should go straight from the thread holder to the pre-tensioner (the thing with 3 holes in it). Your thread should be going down in ALL 3 HOLES. (If you use just 2 like in the manual the thread screws up) It should be down hole 1, back up and down hole 2, back up and down hole 3 Thread should be wrapping around the tensioner. When you thread the machine, make sure the pressure foot is in the up position. Make sure you have your thread completely seated in the tension disks AND you are going around the check spring, then under the hook and up into the needle take up. Also, if you have changed your needle the eye of the needle goes side to side not front to back. Also, the FLAT SIDE of the needle shaft goes to the right.
Let me know if this doesn't help and I'll check it out better.
GOOD LUCK, those are DYNAMITE machines!