problem with 505super I bale size

[scf84]

baled couple bales other day with my 505 super i and i could not make a full bale, it would start making a racket and noticed
the idler in center of pic with chrome spring was raised up and the chain was so loose it was skipping.
what is causing this?

also that back sprocket looks wore out, but it is not.

 

[Nesikep]

Insufficient tension on that small spring perhaps? it should be the slack side of the chain, and it shouldn't need that much tension... however iif the chain and sprockets are worn it can lift the chain over the teeth. Does the idler arm move freely? The only other thing I could think of is that something is dragging really hard and putting an undue load on that chain.. too high a bale tension, seized bearings somewhere, etc.