"Needle Sensor Failure on Walk"

I've been merrily quilting away - having a grand time with the project I posted about yesterday. 

Suddenly the sound coming from the area of the needle wasn't the same.  Experience has taught me that's not a good thing - so I stopped and looked closely. Yup.  The stitches on top looked "wrong", and on inspecting the back, I could see a birds-nest of long threads dangling loosely.  Fortunately I stopped immediately when I heard the sound, so there was only about an inch or so to pick out.

I pulled the bobbin case out, expecting that the thread had slipped out of the little metal clip on the side (which will cause the birds-nest problem), but no... the bobbin looked fine.  Hm...   So I popped it back in, did a little test quilting on a scrap piece I use for this purpose - and well, the stitches looked fine.  So I went back into the quilt and continued working. 

Half an hour later, as I was nearing the end of the quilting, the machine suddenly jammed and the screen on the longarm showed the error message "Needle Sensor Failure on Walk".  I pulled out my user manual and checked the troubleshooting section - but there isn't any mention of this error message.  Looking at the stitching, I could see that the last 2 inches or so were "birds-nest" stitches again. 

Again I checked the bobbin case - nothing obviously wrong there.  I turned the hand wheel on the back of the machine to manually raise and lower the needle - not seeing any problem there.  So I reloaded the bobbin case - grabbed my test scrap and tried stitching... the machine was working again.

I finished the quilting without further incident but became worried that something really bad was wrong.

A search on Google gave me some clues.  Apparently that error can be caused by a number of things, including:

• bent needle
• foreign objects stuck in or around the bobbin case (such as a broken needle tip)
• loose, stray threads around the bobbin case

At this point, my theory is that I've experienced that last problem - and that removing the bobbin case dislodged whatever was in there.  Just to be certain, I removed the pressure plate and had a look at workings inside.  There was a little bit of "gunk" - lint stuck to it with oil - so I wiped the area down.

That seems to have taken care of the problem.  Got my fingers crossed.