Which oring is blowing? I would assume it is the oring on the bonnet that seals when screwed into the ASA. Check for sharp edges in your ASA where the oring starts to seal as you screw the bottle in. If the ASA causes the pin to be depressed before the oring is fully engaged on a flat surface, it can push the oring against the shart edge and cut it. Even if the pin is properly engaging, the same thing can happen when you unscrew the tank, because the ASA is fully pressurized. It might have worked before, but the new higher pressure may be giving the extra push to make the cut on the oring.
Except for the Automag in front, its usually the man behind the equipment that counts.