I have had this same machine I got as a gift this past Christmas. I have not had any problems with the thread bunching up on the back. I had heard about this and asked they dealer. They acknowledged that there had been this problem w/ older versions of this model, but they had since been resolved. They did say that correct threading of the machine and bobbin caused many of the problems. The machine is a little tricky to thread (the white on white markings are not much help to my bifocaled eyes!!), but fine once you get the hang of it. I love this machine. I have 3 Vikings, and a Bernina serger. This Pfaff has become my favorite.