My Weaver Standard Action upright player does this with some longer
rolls (roll stops or pauses usually in the last quarter of a large
roll).  In the case of my piano, it's due to the paper already on the
take-up spool not being wound tight enough.  All I have to do is to hold
the feed spool (upper spool) with my hand, to keep it from turning,
while continuing to pump for a few seconds until the take-up spool winds
its paper tight.  Then I continue playing.  I never have to do this more
than once in a roll.

I occasionally have had the pausing problem occur with new QRS XP rolls
("Wizard of Oz" medley in particular), but it most often occurs in those
huge old classical rolls or stage-show medleys from the 'teens and early
20's.  I usually figure out a natural place in the second half of my
favorite rolls where a pause of a moment or so will fit in naturally.
Then I mark the place to remind me to hold and tighten there in future
performances.

Here's the strange thing: these vintage large rolls almost never had the
pause problem the first time I played them after bringing them home from
a flea market or wherever I purchased them.  Perhaps my piano does not
have enough tension on the upper roll?  Or is it because I rewind them
slowly and without much tension, in order to avoid damaging rolls in
rewind?

Another cause of the problem James Farris described could be from too
much suction (i.e. pumping too hard), thus causing the roll paper to be
drawn too tightly to the tracker bar when only a few perforations are
being played in a given section of a tune.

Jim Canavan
Alexandria, VA
jcanavan10@comcast.net.geentroep