Depend on the materials that u r using,,,, and size needles ,,I have found that different size needle are use for different fabrics,,also sometime there can be a little dust or threads found in the threader where you thread your machine and in the bobbins case have to be blow out often after each use,,, then the staberlizer that you use, if using the sticky they tend to cause the gum from the glue to stick to your needle while sewing and that catches the threads from bobbins and mess up the designs,,,, using wss sometime have to double while sewing ect,, and sometime when the fabrics is not taunt enough in the hoops is causes the designs to dense up.... also another things is the threads size and quality of it make a different but as for the racket you hear on your machine could be needle bent or position not set properly,,or timer could be off,,,, I have learn to call my dealer on many occasion with minors details ,,Own Babylock ese2 Babylock Elegante , 3 Treadle Singer,, And a Singer in a case that not have been classfied (don`t know what it is but pretty)and serveral more... But call your dealer or go onlines you shouldn`t be haven`t this much of a an headache hun.....God Bless Ya,,,, ( not a know it all just learns as I go) hope this help sweetie