I had a similar problem and with mine I had to make a minor adjustment so that the needle did not strike the foot itself.

I think you can figure this out and sounds like you are well on your way. Need to put on your detective hat right away when it happens. Did you check when it happened that the needle was loose? All walking foots I know of work that way and I have never had a problem with it loosenin the set screw for the needle.

I would think it is either you moving the quilt too fast that you bend the needle just enough that it is hitting the plate. Look for marks there. You could have some dings that you want to make sure there isn't burrs that may cut thread in the future. Also look at your bobbin case to see if the needle may be striking there.

Sounds like maybe cjsews has the answer for you too.

Good luck and you don't want to be doing this to your machine too often or you may be going to the repair man.

I have a janome which can be temperamental as yours is. Try completely retreading with a different thread top and if necessary bottom. It just happens some machines dislike certain threads. A fussy child.
Also. Use that sewing fine oil and put a couple of drops on the cone and needle wipe down and wipe around bobbin case. This is not just machine oil. Can't find mine and forgot name.

Sewers aid. Find a local supplier and buy a bottle. I did a class with a professional quilter and the tip on drops on cone came from her. Also the stroke he needle and bobbin case. It definitely helps ven if it doesn't solve this problem.
Maureen.

What kind of needles are you using? Are they for quilting or sewing? There are so many variables. I hope you figure it out.

I've used that sort of walking foot on my Janome and am wondering if you are installing it correctly?
You mention that you bring the bar forward ... to me it goes backwards and over.
From the picture you ahve shown the little bar that is coming forward is the one that you can have on (or not) to use as a guide for distance between stitching lines.

There are indeed a lot of variables for possibilities, and with none of us being there IRL, it's like taking stabs in the dark.

ITA with others ... take the machine and foot into your dealer and ask for their help.

Thanks for feedback, I decided to order another walking foot since the problem only seems to happen when I use current walking foot. If needle breaks with new foot then I will know that problem must be with the machine itself, and getting a service is the only way forward.

In meantime I can't face breaking a brand new needle so have decided to make another quilt top before testing the new foot (I hope you appreciate my logic). I may be asking for inspiration in a second. :)