My Janome Memorycraft 11000 is acting up. I've had the bobbin case and retainer replaced 3 times now. All of a sudden the machine starts making a weird noise and next thing I know the thread is bunched up underneath the fabric and the bobbin case has literally been picked up and turned wrong in the retainer. I'm also having problems with it just stopping in the middle of sewing while I still have the presser foot engaged. I've even had it doing the opposite as well. It will sometimes continue sewing when I lift my foot off the presser foot. I fear the folks at this repair shop don't know how to fix it. If any of you have experienced any of this and it has been repaired. Maybe you could let me know what the problem was that caused the malfunctioning.

I'm frustrated because all they're doing is replacing the bobbin case and retainer rather than trying to figure out what's causing the problem.