Make sure you have all the pickup teeth. On the 504f I'm using now, adjusting (then replacing) the springs on the sides to get the pickup teeth within 2 inches of the starting roller was the trick for me. It would be nothing to plug 1 out of two bale starts. The springs were weak from age and when I ran out of adjustment, I replaced them. Last time I baled, I did 39 rolls in 2.5 hours without a bit of problems.
That gets the starting chamber geometry correct and boy does it work now! Next up is new starting roller belts which seem pretty slick. That should help with the courser Johnson grass on second cut.