I've had my Avenger 25 for a few months now and have shot a few 100 pellets through it. My favorite rifle. Unfortunately today when I pulled it out of the gun bag and attempted to fill it with air, I discovered it won't keep pressure in the fill tank and you can hear air leaking out inside the rifle close to the trigger. I'm assuming one the internal seals is broken or needs a replacement O-ring. Any ideas on what might be the issue? Any suggestions or pointers on how to disassembly and repair it myself? Any repair videos? Thanks in advance.