I have a 710 and had problems sewing with it. I asked on a FaceBook site for Bernina 700 Series Owners. If you are on Face Book you might consider joining this one. Anyway, it turned out I wasn't giving mine enough oil. It took 8 drops but still wasn't sewing properly, so 2 days later I added 12 more drops. That is a total of 20 drops and this was only a couple weeks after being serviced. These machines are thirsty. So my advice to you is to add one drop at a time and if there is room for one more, add it until it looks filled up! If you need help with where to add the oil here is a YouTube video that might help:
https://www.youtube.com/watch?v=XBKN7pilzyc They show it taking only one drop of oil but trust me, it takes more.