Yeah, its out of adjustment. Have a friend cycle the baler through a knotting cycle, by turning the flywheel by hand. You stand at the back by the knotter and watch what happens, being mindful of which side works fine and which side doesn't. Make note of what the bad side is doing that is different than the good side, and adjust it so they are the same.
Kind of like the old joke, of the guy with a withered hand, and asks, "Please Lord, make my hand like the other." So ZAP- now they are both bad.