Ignoramus11878 fired this volley in
:

I think that there is a pressure loss at the Schrader valve or some
such, like a spring that needs to be pushed by air.

Not when a chuck is engaged on a Schrader, no. Both the chuck's valve and
the Schrader valve are fully opened when fully engaged.

More likely is a bad face washer in the chuck, causing a leak. An
expanding-collar lock-on chuck can solve that, and make the job easier,
too.

Lloyd