I don't have a Janome, so I can't give you specifics...I can tell you I had the same issues, and I was so upset, almost giving up...and I am not a quitter....I finally ordered in different fmq feet than what came with my machine...found out they are smaller, and therefore they hold the fabric correctly for fmq, no more needle beakage, thread breakage, or icky stitching on the back and taking out all of it...so, maybe that is a suggestion?? I am sending you a quilt hug, and I know there will be some veteran fmqer's come along to help you...
Take care,
Kif
PS I have a post on here about it, too...
http://www.quiltingboard.com/t-153683-1.htm