That's a great tip quiltstringz!
I do agree that sometimes it's maintenance required in the bobbincase / hook area, but in most cases for me it's been an unbalanced stitch and usually the top thread has been the problem. I have had loops top and bottom from top thread. Before I start a quilt now, I usually lay a small piece of fabric over the batting left over on the edges and test sew -fast- loops and sharp fast zig zags to adjust my tension on the LA. It shows up eyelashing and tight tension really quickly this way. Then I reduce both tensions to the point where there isn't any "pulling" of the fabric at the zig zags, and quilt my heart out on the main event.
The loops can also be from backlash. Are you using magnaglide bobbins or regular? Do you have a backlash spring in your bobbin case? Are they only at direction changes or logical "stops"?
I wrote a couple of posts on my blog last week about tension. Longarms are no different - in principle - when it comes to tension than a domestic, just a little more spectacular about highlighting a tension problem, because there are so many examples in such a short amount of time. If the mods don't think it's trying to drive traffic to my site, I will post the links.