Lesson learned: when the sewing machine is acting up and producing odd quilting, stop and take it in for diagnosis and reapir.
I have spent more time than I want to recall ripping out a LOT of poorly formed machine stitched motifs in a quuen sized quilt. It was clear that there was trouble when I put them in but apparently I was not engaging in good quality control (I was at retreat, not a grat excuse but the best I've got).
The good news: my bobbin case has been replaced. The bad motifs are all GONE and the deadline for this gift moved 3 months in my favor. Oh, and I have significantly practiced my ripping skills.
Phew!
Mary