Daystate Revere lost air pressure after changing transfer port rings, steer me to a fix

I changed out my transfer port orings day before yesterday on my wife's regulated Revere .177 due to one of them blowing out. All was good after replacing them, no more air blowing out the breech and a 20 shot string showed normal velocities and SDs again. Just took the gun out today to get it ready for a FT match and saw the tank gauge had fallen to zero (it was probably above 200 bar when I put it away) but the regulator gauge was still showing about normal pressure.

When I replaced the transfer port orings I did partially unscrew the regulator gauge to de-gas the rifle but retightened it afterwards. So...thinking maybe that could be the problem and I should change the regulator gauge oring? Or could it be something I did changing out the transfer port orings? Would appreciate any advice on the matter.