Pfaff 1222 and pfaff 1229

Question

I have pfaff 1222 and 1229 and they both have the same problem. They sometimes work for a few minutes and then stop, then will start working again the wheel is turned manually. Mostly they just aren''t working. I had the foot peddle fixed for the 1229 but the machine still not working so it is not the foot peddle.