I have a Bernina 820 and haven't had a problem moving backwards when FMQ. It may be that your speed and hand movement aren't "synchronized", but that doesn't seem to be the problem since the stitches are okay when you're moving forward. Hopefully your Bernina dealer can help, but I discovered (too late) that my dealer knows little to nothing about solving the various problems encountered when piecing or quilting, so I've had to solve most of my problems with trial and error. Are you using the BSR? I used it a couple of times and wasn't at all happy with it, so it's been in its box for two years! There's a Bernina 800 series Yahoo group that you can join that may be able to help. Just google Bernina 800 series and it should get you there.