Both bellows are probably leaking. These things decompose at the spot where the rubber is fastened to the plastic block. On a 212, they're not too difficult. You can just wiggle the old, deflated bag out and the new, inflated one in; no arms need to be undone. The one and only real challenge is that the lower plastic block's holder in the lower arm can be somewhat snug at times. I use an air chisel to get them free, but not everyone has that luxury