Thinking about it some more, make sure stripper arm is tight against billhook, may have to take a hammer to bend it up so that it slightly rubs the back of the billhook.  This is the green arrow in my picture below.  If the tails on the good knots are too short they can pull apart, that goes back to twine tension.  If the knotters are getting wore, you may have to adjust the twine disc somewhat, I usually guess and check.  Loosen the nut (bottom red arrow in picture) and bump the gears a slight amount to advance or retard the twine discs (top red arrow in the picture).  The second picture is the tails I am talking about on knots.  This one is too short in my opinion.

(100_0270.JPG)

(100_0269.JPG)

100_0270.JPG (125KB - 409 downloads)

100_0269.JPG (105KB - 402 downloads)