My dealer and trainer came to the house. They replaced my bobbin case. They adjusted the tension, but it wasn't way out of whack, maybe 4-5 full turns I think. The trainer taught me how to notice if it's even a little off so I can adjust it before it gets too bad. They adjusted the take up bar just a bit and did several other diagnostic tests that were fine. They watched me thread the machine and out the bobbin in. After some test free motion quilting, we finished the computerized design on the quilt I'd started. There were no tension problems. For lack of no obvious explanations, I suppose maybe my bobbin case was somehow messed up. The squiggly piece on top was sticking out further than the new one, so maybe that was the problem.
I've got another quilt ready to load, hopefully this weekend, so I can get right into another to make sure it's still working well. Fingers crossed that maybe now I'll be able to focus my energy on improving my skill rather than fighting the machine!