Rodney, my first long arm had a serious problem with thread "unthreading" from those "self threading" eyes. It came with some with shrinkwrap on to close them, and I had DH bend one more to make it closed.
When someone had repeated problems with thread breaking - it was recommended they would video the machine in use, and often it wasn't a real tension problem, but that the thread would fly around and hook on something or come out of a guide and get messed up. Some thread has more "spool memory" than others - like metallic or some monofiliment - and it wants to curl up and get in all kinds of places you don't want it.
I have a real problem using Coats & Clark made in Mexico thread on my White 670. For some reason, that stuff wants to loop down and there is just enough of it when the thread uptake lever comes down, that it can get under the long bar coming off the tension (that is there to keep this from happening) and then it will snap right at that point. If I slow down (satin stitching on yards and yards of ribbon) it does not happen, but at higher speed it will do it regularly. I bought a couple of spools at Walmart, and both colors gave me problems, but so far no other thread has done that. I still have to use quite a bit of it, so I was thinking of putting some tape on that bar to make it effectively longer.