My guess is that your player stack has lead tubing and a transposing
tracker bar, such as, Simplex or Amphion.  Between the tracker bar and
the lead tubes is a short section of rubber tubing which normally allows
the tracker bar to move back and forth.  We have found a few cases where
the younger generation has forced the transposing lever sufficiently to
move the tracker bar.  This shatters all that OLD rubber tubing that
hasn't moved for years.  The result would be that all the hammers move
towards the strings when playing.

Solution:  Remove the upper and lower covers just in back of the tracker
bar.  This will expose the shattered rubber tubing.  Remove all remaining
rubber tubing and replace with new tubing.  When re-tubing, be sure to
shift the tracker bar to the right when replacing left side tubing and
then shift to the left when replacing right side tubing.

Another possible reason for the problem would be a separate bleed chest
with an air-supply-to-pump vacuum.  If the supply to the pump is
restricted or lost, this would allow all the pouches to activate,
causing the same problem.  The only place we've ever seen this problem
is on a bleed bar behind the tracker bar on an Apollo player grand.

Bob Lemon