I had always assumed that this was battle damage, although I have no way of confirming. The Hellcats were used quite extensively in a ground attack fighter-bomber role especially during Operation "DRAGOON" in southern France, and used to pick up quite a bit of flak/AA damage.
I recall my father saying that the Hellcats were very popular with pilots because of their ability to absorb quite a bit of damage and still make it back, and also their relative ease/straightforwardness of landing. Just cut the power at the appropriate time and "bang" you're down he used to say. Apparently one of the least popular FAA fighters was the Seafire which was notoriously difficult to land with its narrow undercarriage, and also its tendency to glide over the deck and not catch the wire.
Cheers
pemcg