Oh dear. That sounds like the sort of problem they had with this type of pistol when it was first introduced as the PR15. I had one back in 1989 and it leeked. I swapped it at the shop for a Crossman 1322 at the time. I thought that they had fixed the problems though as I bought a second hand Compact a couple of years ago and it has been perfect. A really great value pistol. I guess it might be worth giving it a squirt of Pelgun Oil and see if that make it seal. However, it could be that there is a small burr somewhere which has sliced the O ring on assembly. Such a shame that these sort of faults find their way out of the factories still.

ATB
Andy.