Sewing Rose-----Can you describe the problem that you had that the dealer could not figure out, but you finally found it yourself?  What did you do to fix the problem?  I am sure others who are on this Group would like to know, too.   I am happy to report that my problematic MC500E with its bouncing, noisy bobbin has been working well--and quietly- since I got it back home. I have used the embroidery machine almost every day since I got it back.  
Kathy Strabel   Camas WA