My brother has an Air Venturi Avenger that recently developed a strange problem. AS the air pressure in the tank gets anything below 2500, the reg (set at 1900PSI) will immediately start to creep downward with the bottle pressure. It actually goes as low as 1100 PSI, with the tank pressure showing much higher, causing obvious problems. He should still have a 600# cushion left the way I see it. I'm thinking a possible bad or very inaccurate tank gauge, reading higher than it actually is ?? Your thoughts ? I'm not too familiar with this model. I've only handled his a few times. I don't know what else would make the reg lose it's set point. Your thoughts ??