Sam Harris was asking for suggestions as to his problem with a couple of
striker pneumatics on a Standard double valve player.  It wasn't too
clear to me whether he was saying that at very low vacuum, it would work,
or not.  As I understand the problem, the valves simply don't move when
their respective trackerbar holes are uncovered.

There is probably two reasons this could happen in a double valve
Standard.  Assuming he tested everything on the bench first, IF he tested
it separately, apart -- then he checked primaries separately and
secondaries separately.  So thinking that possibly he missed a couple of
gasket holes there, I would opt to bet that despite all his precautions,
he has a stopped channel hole from the primary to the secondary.

Assuming that he checked everything assembled as well -- on the bench --
here are some additional ideas:

1. The two valves in question have been reset in such a way that when the
pneumatic shelves are replaced, the ends of the valve stems are bumping
the hinge end of the pneumatics.  (My first guess) Interference.

2. The valve stems are too short at the ends, and don't go all the way
through the outside guides, so they are jamming, until he lays this stack
on its back to test.  Then they work.

3. The proximity of the notes (A & B) means there is one note in-between.
So possibly there is a connection, like a crack.  Say, for example, you
have a crack that channels the two valves.  Unless both notes play at the
same time, neither note will play, being held down by the other valve's
primary valve.

Craig Brougher