Just pumped up another tire with a removalbe presta valve. When pressure reached 100psi, all the air came back thru the valve and pressure was lost. Tried using 2 other pumps and got the lung effect. 5 psi, 0, 5 psi , 0.

So then I turned on my air compressor and screwed on a presta to schrader adaptor. The top of the presta stem free floated in the adaptor. Used the chuck to air up the tire. As soon as the chuck was removed, the tire deflated.

Problem = PRESTA VALVE, not the pumps or compressor.

Removed the tight valve using a wrench. Cleaned the inside of the stem with a pipe cleaner & screwed in a new valve stem. Same results. Now this tube had been patched several times and inflated at least weekly over its life.

My opinion: Tubes with removable presta valve cores have a limited life.
Imagine some poor soul with this problem on the road and tries to inflate the tire using $4 Co2 cartridges. Kiss those goodbye.
Anyway, I have a new tube with a smooth OD valve stem to install.