My one-month old .22 700 cm Panthera developed a serious leak through the Valve Holder. This is Part X1-1 on the FX Panthera schematic.. The Valve Holder contains a very small internal o-ring - Part X1-2. The Valve Rod - Part X1-6 moves back and forth following each hammer strike and is sealed by the small o-ring.
According to other posts, the Valve Rod is susceptible to bending and, once bent, the o-ring will no longer seal.
Accessing the Valve Holder to verify the leak only requires removing the chassis. However, removing the Valve Holder for repair to internal parts requires disassembly of the Plenum and special tool or, in the alternative, a bit of ingenuity as shown on Earnest's video on Panthera disassembly.
Again, my Panthera is only one month old and I could have sent it back for warranty repair. However, that would involve paying for two way shipping and a wait of indeterminate time. So, I just ordered the necessary parts for approximately $45.00 and am hoping for the best.
JackHughs