Shooting the pp700 today and it began leaking from fill probe opening. Removed air tube, removed end cap, removed single screw from end cap that holds o-ring in place, and reassembled. Back to shooting in less than 10 minutes. Simple is good.
The same thing happened to mine...it was shooting so well that I dreaded taking it apart. But like you said, it was a quick fix and it was back up and going in short order.
The OEM O-rings simply seem to be too soft in a variety of places. The fill port O-ring and the breech block O-ring were two notable examples.
Agree that they are too soft. My fill port o-ring was just abraded away in one area from movement. I changed my breech arrangement long ago and eliminated the small stock o-ring there.