My Bernina repair man told me, to wind the bobbin one more loop around the post before it gets wrapped onto the bobbin, and that really solved my problem....my stitching looked very much like yours - I found anytime I have issues with tension - I first rethread the top of the machine, and find the machine doesn't like the fabric or the top and bottom threads don't work together well. I have started using "Glide thread" and have no more issues.