I have a Pfaff - not that model, but I do know that they can be very picky machines. I can only use good thread (Coats and Clarks will get in there and freeze the whole thing up). I also have to be careful about cleaning off the lint every time I use it. Guess it forces a good habit. I use pre-wound bobbins all the time (I'm lazy about bobbin winding) and have never had a problem with them.
My repair shop guy told me that every Pfaff has it's own personality. Mine is a diva, but I lover her anyway.