If the tension on a Bernina machine is adjusted correctly, why would I ever want to adjust it? If I am having trouble with my stitch, then I take it in for adjustment. I have had my Bernina B380 for almost a year and have sewed a great deal on it in that time. My stitch is the same as when it was new and I have used several kinds and weights of thread on it. After its annual servicing, if the stitch isn't right, I will take it back until it is right. When the first technician who adjusted your bobbin loose was finished, was your stitch correct? You don't explain why you took your machine to another technician. If the technician is certified, I would take the machine back until it is right. They should guarantee their work for at least 60 days. I would only take it to another certified technician if I was unable to get a satisfactory result. It sounds like your adjustment is incorrect if the stitch is gathering. It shouldn't do this. When you take it back to correct the problem, perhaps to the technician who adjusted it last, make sure that you sew on it for a while before you leave the store so that you know the stitch is correct. The stitch should be just as it was when your machine was new.