James Farris wrote of a problem with the roll stopping when playing a
jumbo roll.  It's very difficult to diagnose a problem "hands off," but
the first thing I would check is the spring on the governor-control
bellows.  The spring may be extremely weak (unlikely) or may be broken
or missing altogether.  As you pump, the bellows normally closes so
that the motor does not speed up.  If the spring is missing, the bellows
would continue to close, and on a long roll would close completely.  On
a normal roll there isn't enough time for it to close completely.  The
reason it plays again, after a brief pumping break, is that the covering
cloth itself acts like a weak spring to open the bellows, but it quickly
closes again when you start to pump.

Don Cox