Looks like the same breech as the CP1, CR600, PR900, etc. Here’s my fix:https://www.gatewaytoairguns.org/GTA/index.php?topic=137412.msg1377636#msg1377636
If you take a flash light to the chamber area you will see the oring. My barrel does not seem perfectly flush. Seems to almost be a small gap in there just past the oring. My pellets seem to rock nose down as they enter. Let us know if you learn anything new.
Mines going back too, they said they would be sending a shipping label.