I really need some help.  My old Rex 11-155R has been working Great for years.  It sat idle for a few months and then when I went out to the shop to do a job...The Stitch it made was almost 3/8" long and the Adjustment Knob would NOT work.  Knob functions as designed but...Stitch Length remains at 9mm or bigger.  I removed the top and back access plates as well as the Knob assembly and for the Life of me cannot figure out how it is supposed to work.  I searched the interior of the machine and fo