Was the dryer and hoses cleaned properly from the last job? I know you said you cleaned the screw and barrel, but how about the feed throat from the hopper into the press? Usually it's a square with circular opening. Under and around that circular opening there's creases. If you rub your finger inside of there, there's usually always some build up that will randomly get pulled into the new material.

Fairly difficult to see the defects - but why the 50 degree jump from rear to front zones? Does it freeze off if lowered at the tip / front?