I have a Pfaff 7550 that I dearly love, purchased new in 1994. I also just recently bought a Pfaff 1471 used, paid $50, because the people thought it was broken. The previous owners were asking $100 for this "broken" machine. I offered them the friendly, helpful advice that if they watched some You Tube videos and oiled the machine they could probably get $300 or more for it. I then said I had $50 to spend and if they wanted that money, I would buy it. I couldn't pay more because I was risking the possibility that I was wrong. So I bought the machine -- for $50. I oiled it. It purrs like a kitten.
Both of my machines are about 20 years old or older.
My instinct right now is that few machines on the market these days are even close to as good as the old ones. The new ones may have computers in them, but they suck and die in a short time. (I know even with my 7550 that the mother board can go out and I'll be sad, which is why I bought a backup.).
Pfaff is especially bad for quality control right now. I wouldn't touch them with a 10 foot pole. Yes, you can get a good one, but judging by how many relatively new Pfaffs I am finding on the used market, I suspect they're putting out a whole bunch of lemons.
There is a repair person named Kenn, who fixes machines on the side, I think. I've watched some of his You Tube videos and have been impressed with what he can do. He can repair 7550 motherboards and such. He may have an inkling of what is wrong with this machine. His web site is here:
http://www.kennsplace.com/.
So my advice:
1. Perhaps talked to Kenn at Kennsplace. See if he might give you a lead.
2. Dump this thing and buy something else. Sell this one for parts. Buy a used machine if possible.
The old adage that they don't make em like they used to really, really holds true with sewing machines...
I will never buy a new machine again. Ever.
Good luck!