@MountainRider. More than likely you have a bent stem on the valve core which prevents the stem from riding back up and allowing the seat to set after airing the tire up. I've had that happen when I used an airhose with a long stem pin in the air chuck. Now I carry a couple of extra valve cores and a core removing tool because i just replaced the ones on my trailer after coming back from my recent trip. Had to fight the air dump problem. Fill tire up 15-20psi above target point then install the valve cap real quick. I have either a TPMS cap or metal caps with o-rings for just this reason.