Upper Thread sensor

Kathy Strabel

Hello--Group--I hope all are being safe and healthy as we wait out the pandemic. 
I wrote in a couple weeks ago about some thread breakage and the MC500e machine not telling me there was a thread break and the needle not stopping. I have been stitching OK in the meantime...but today I actually had a tread break, and the needle just kept on stitching and I did not get the warning on the screen about a thread break. I just noticed a slight change in the sound of the stitching, then realized there was the thread break and no warning and/or no needle stopping. I thought maybe the thread sensor somehow got turned off, but no, it is ON. I turned it off, waited a little bit, then turned it back ON, just for good measure, but no difference.   I thought I was in the clear, because I have totally eliminated the thread that was breaking so often, and I did not have another thread break until today. This time, I was using a thread that my machine likes, and has given me absolutely no problems for many many months, and not a new spool of it.  Today's break was just one of those things that happens from time to time. question is this: since the upper thread sensor is turned ON but not alerting me that a break has occurred and also not stopping the needle from continuing to "stitch" with no thread.....what else could this be?  I have scraped the thread path with a dollar bill, and done the "flossing" with  a heavier-weight thread doubled over and pulling it through the thread path. Any other suggestions??? 
Thanks so much, and --be safe and healthy out there!!!
Kathy Strabel    Camas WA