I have the NX-2000 Also and have that knotting problem as well.

After I do needle down and then up to catch the bobbin thread, I have a habit of pulling the bobbin thread to the back under my presser foot with a right angle tweezer tool. Never a problem.

Thanks again for everyone's thoughts. The problem is RESOlVED. There is NO Issue with Aurifil, it was a mistake we made with the spool cap, that's all. The auto cutter works beautifully, the auto lock stitch works perfectly and the machines runs beautifully when we put the right spool cap on.

My wife loves the auto lock stitch at the beginning and end of sewing, the auto cutter and the automatic foot lifter. Features that we paid for and are enjoying. She has no desire to do it manually when the machine works so well as long as we use the correct spool cap.