CAUSES MACHINE TROUBLES 1. Seams pucker A. insufficient oil and loose screw B. Bent needle and wrongly attached needle 2. Lower thread breaks 3. Looping stitches C. too heavy pressure on the presser foot D. Improper winding of the bobbin 4. Machine to run noisily E. improper threading and unbalanced upper and lower threading 5. Skipping stitches​