Only thing I can think of is their a cable underneath? Might it have started fraying?
What size baler are you running? If you are running big round bales, you are possibly over working it. A baler takes more and more hp as the round bale grows. Many folks will make smaller diameter bales if they are low on hp. My buddy says he can bog down his Deere or IH (99 and 105 hp respectively) by trying to bale a max diameter 6' bale on his deere 566 baler. A 5420 only has 65 PTO hp, don't some balers have a clutch in them to protect the tractor?