I have free motioned quilted for years. Before my 820 Bernina died I had really good stitches. There are problems with many 820's and they offered a $2,000 credit to turn this machine in. The stitches look good with the Bernina 770 QE on dark fabric and dark thread OR light fabric with light thread. This makes no sense. I now use a Superior 80/20 topstitch needle with cotton and steel thread. Have tried all kinds of needles and thread (to include Aurifil and mettler cotton plus others) with no resolution. You can send email to Bernina but don't get a response. to Bernina. I welcome all replies and thank you.

Oh no! I have the 770QE and it makes beautiful stitches!
What do the people at your Bernina shop say? They need to help you out with this.

Have you taken the fabric you are working with into the shop and showed them how you were getting the feathering? I have had to do that with a couple of machines that I had. After they saw what I was trying to do they were very helpful in getting it fixed. Turned out there was a burr somewhere on the machine that had to be sanded down. One time it was the way I was winding the bobbin. You just never know.

I have an older Bernina. Hope you can get it resolved. What has the store said about the problem?