this is  an old thread,   but   the first thing I'd check is  the  bypass on the  rollers.   

a lot of  'fluff'   will wrap around them,   stalling them dead if the bypass is  set too light.
part of this is  watching  the amount of  fluff on the  side of the bale as it's  unrolling.. when it gets  sizable,  it's  time to reverse direction.   I usually   reverse  and  run the opposite direction  until the fluff  builds up on the other side... then  reverse it again.

sometimes   getting a full  rotation is impossible,  and  all you can do it  go back and forth.  

Managing the  twine build up  also helps with air flow/amount of bite the  flails can  grab.. 

lastly,   you need that bale to turn faster than  what the  flails  bite off.    you have to run  full flow oil at the tractor.  

Some  types of forage  respond better by  processing  in the opposite direction it was rolled up. Some better with  processing  the same direction.  


   After  a couple 1000 bales, you'll have it figured out.  
I've  'rebaled'   a lot of  old,  rotted-off-string bales   (mostly grass)  back into shippable  round bales.
The  processed hay will be shorter stemmed,  and  a lot harder to form a core in the  baler. Straw  will be a little harder as it's  'slick'.   The neat thing is you can  process 2 bales into 1 brand new one... they will be a  LOT heavier.     I imagine a  small square baler wouldn't be near as  finicky.    


LOL,  just don't  process  a lot on a windy day!