Not wanting to hijack another thread, I am starting a new one. In a recent thread about unbalanced stitching, Wizcrafts made this comment:  "Keep an eye on the thread as it unwinds from the spool. Follow the thread as it makes its way to the top tensioner disks. Watch for any sign of binding as the thread comes of the spool. Watch out for twisting that forms loops and knots in the top thread. Either of these things will increase the top tension temporarily, causing the knots to move up."