There is another way to adjust the bobbin tension, it's a little tool that will turn a screw or (star shaped) something similar to the left or right. try that one click at a time to just tighten it a little bit. See how it stitches. If that works great.
If not, I think this may be a speed issue as this looks like its happening in the same spots on the motif.
It also might be start/stops and that's a matter of practice.
Teri

Hello everyone,
I'm wondering if anyone can help me with my problem. When I quilt a design on using 2 colors of thread ( in this case I have a burnt orange on top and black in the bobbin). hopefully you can see from the image, the bobbin black thread shows through to the top but not all the time. It's strange because I can do it one time and it doesn't show at all and the next time I do it, it shows. It's very inconsistent. Does anyone know what I can do to stop this from happening? Its almost like a sequence of events has to occur just right to prevent it from happening which I'm apparently doing by accident because I can't always repeat it and then it stops working again. I tried changing the needle and I've lowered my tension down to 2.0 which helped the most but as you can see from the image it's still coming through to the top in various places. If I go any lower on the tension it gets too loose. My dealer told me not to thread the bobbin through the small wire hook (when you use the mirror to get it through the clip). They said not to put it through there because it was too much tension. When I tried that it made it a lot worse. Then I was told it was digitizing, which doesn't make sense to me because I can use the same digitized design 10 different times and the problem happens 5 out of the 10 times. So I don't think the digitizing has anything to do with the problem. So I'm at a loss. Don't get me wrong, I absolutely love this machine it's been a dream! But working with 2 colors of thread has been my greatest challenge. I've exhausted everything I can think of short of standing on my head, pointing one foot north and one south, holding my breath and count to 10...

Barb