My F10 is now bleeding air from the very small vent hole shown in the attached photo. I have disassembled the unit, cleaned the two ball bearings, spring and reinstalled the white O-ring. In order to do all that I had to remove the block (manifold)and the backing plate, that is immediately above the burst disk, that holds all the check valve's two ball bearings and spring in place. Anybody else had this problem, I posted about this awhile back and one person came back with cleaning the check valve with WD40. I did that and it did not help.