You could also check with the Viking MegaQuilter yahoo group (
https://groups.yahoo.com/neo/groups/...gaQuilter/info)
They have lots of helpful information, mostly for the model machine that you have.
And yes, it IS frustrating when the user manuals don't have enough information. I'm on both the yahoo group listed above, AND one that is for the larger VMQ18x8. Thank goodness for the internet and Yahoo groups and the Quilting Board - otherwise, we'd all be very upset with our tools/toys.
And, yes, I had a very similar situation with the thread breaking - I'd be stitching along just fine, then for no apparent reason, the thread would break. Again, in this case, it was some bad thread. I tried using it for piecing, and still had the same issue. Gave it away to a hand quilter.
My personal preference for my longarm is Aurifil or Superior threads. The other stuff just does not seem to be as reliable... or at least my machine has a preference for those threads.