Quilting

So... I tried out to quilt on the bargello heart and yet again the thread started to break. I am puzzled at what this is all about. It worked fine on the star table runner, It did quilt lovely and the thread didn't break once. When sitting there thinking I thought what if I turn over and quilt from the back since it is an over all pattern I am doing. So I did and quilted it without a hitch. Am now wondering if it is the backing giving me so much trouble. I have a fleece backing on both of the quilts but the one that quilted nicely the fleece is a softer and shorter fleece then the black one that is on this one. But still the center part of this quilt went together without a hitch so something must have happened to my machine but what? I really don't know what to do with it. I am going to quilt some more and then try it out on some other projects as well but if it still is fussing with other backings and batting then I will want a new machine.   But somehow I think that will be a huge struggle with my dealer, since she wasn't very helpful before.