Has anyone else had this experience? I found that I couldn't top up the pressure in high-pressure tires that are down only a few pounds unless I release a lot of air first.

Example: If a 130 psi tire is about 10-20 pounds low, I experience a "lock-out" condition with my Topeak Joe Blow floor pump until I release another 20 pounds or so. If I get the tire down to 80-90 psi, I can then add air. The lock-out means I can put my full weight on the pump handle, but nothing gets through the valve. The pump's gauge goes way up as if the tire valve core were screwed shut. Initially, I actually thought the core was frozen shut, but it's apparently just the amount of pressure still in the tire that keeps the valve from opening.

Once I learned that I needed to release pressure in order to add pressure, it wasn't a problem - just another step in the inflation process. (I'm sharing this earth-shattering discovery because I have nothing more profound to contemplate at the moment.)