Niels,  There are a number of situations that could cause notes not
to play or to play very weakly.  This is just a quick list off the
top of my head and is not exhaustive.  It should get you thinking
in the right direction.

1. Clogged trackerbar: use a tracker bar pump first to see if it is
clogged with paper.

2. Problems with the striking pneumatic and/or it's cloth:
(a) unglued, (b) porous, (c) rat-eaten, (d) split

3. Could be a problem with the valve or its pouch (insects).

4. Be sure it is the player action and not the actual piano action.

After this message is sent, other ideas are sure to come to mind.
Hopefully our other MMD pros will have covered those bases.

About the larger rolls slipping as they near the end of play --
this is to be expected on player pianos with the brake removed.
As more and more loose paper accumulates on the take-up spool, the
probability of slipping increases.  It does not matter whether your
bleeds are excessive or not -- on a player with perfect bleeds this
will happen.  You must correct this by adjusting the play brake,
thus adding a very small amount of tension on the paper as it plays.
There is very little, if any, chance of harming your rolls if the
tension is light.  You do not want a lot of drag!  Just enough to keep
the paper from accumulating on the take-up spool completely slack.

_Remove the rewind brake!_  Here is where the possibility of damage
exists.

Sam Harris
Greenville, North Carolina