if you dismantle the post..
in the bottom where the shaft enters the air section of the oil pressure stick… there is a tiny little hole that you can insert a needle in to pressurise it..
some of them apparently dont have this hole at all though.. so cant be re-pressurised at all!
the hole in mine was about 1mm and no needles would fit and stay air tight.. so i had to use a micro drill bit and make it 1.2mm..
theres an o-ring inside that blocks off the other end to ‘seal’ it.. but it wouldnt seal on mine no matter what size o-ring i tried..
so my bodge was to put a bit of PU sealant under the o-ring.. put the post back together.. inflate quickly.. leave the needle in for a bit.. take it out.. and the air pressure then forced some sealant into the hole and blocked it..
it will mean i might not be able to pressurise it again.. but its working for now and holds air..