Hi Butch, almost a year old post, but I have 2 of the PPFE models and one started to have the same problem - in my case it turned out that the driving pin (metal rod that pushes the nails up and into the moulding) had worn out, preventing the nail from fully pushing into the wood. There is a ridge on two sides of this part, and normally they protrude further than as shown in the attached photo.
Frankly, I just joined the group today in hopes of finding a replacement part! I've been unsuccessful in finding the part so far, and the company is no longer in business. I'll do a separate post trying to find the part, but thought I'd chime in here.