I use always use Aurofill on my Mega quilter and have no problems at all; this is the thread that Viking recommends for it. You have to make sure it's threaded right; especially at the top when you put it thru those holes; one is skipped. Also it has it's own type of bobbins and you can't wind them on the side winder because it goes the wrong way. I'm not sure where you are located but if you have a dealer around you you might take it into the store and have them to look at it.