About 18 months ago I bought a supposedly new in a box Pfaff 4.2 from local quilt shop which has since closed. It is my second Pfaff. I thought it made an odd clunking sound while doing FMQ but when I took it to a class the people there thought it needed servicing, plus it was skipping stitches. When I took it in for service the technician said that it was so full of thread pieces and lint that the motor was over heating, although I did not a message from the machine. Since I try to clean out my bobbin area with each bobbin change, I was a little surprised to hear this. It was better for a while but now is back to acting up with FMQ. Anyway, my point was, maybe your machine just needs to be taken in for a good cleaning. I feel there are many places in a Pfaff that can't be cleaned at home.