Strange Tank bladder problem..

My pump was cycling, every 5 seconds. So I assumed it was a waterlogged bladder..Shut everything down, closed all the valves, and drained the tank. Tried to put air in the tank, after it was empty. Gauges went up a few pounds, then down to zero.. The bottom drain was still open, and air came out of the drain.
Hole in bladder obviously...????

Closed bottom spigot, added air to 28 lbs. I have a 30/50 setting. Worked perfect, 1.5 min cycle time.
Figured it was working like an old bladder-less tank.
Had a replacement tank, which I knew was good, decided to replace the tank.

Did the same steps,as in the first paragraph, but this time, once all the water drained, I still had 28 psi, with the bottom spigot open.
Even tried blowing air into the bottom spigot, to dislodge a suspected blockage. Still held air...

This has me baffled, how can a bladder leak air, then an hour later hold air..
I have remote gauges, on my setup, so seeing pressures, is not a problem..



The left gauge is the pump pressure...the right, is the tank pressure...

 

So you turned off the pump, opened a water tap, and waited until no water came out.

The gauge on the left is connected to the the same area where the pressure switch and pressure tank are connected.

If those things are correct, I expect either a clogged line to the left gauge or a failure of the left gauge.