Victor -- I do not pass myself off as an expert in these matters, but
having worked on players for over forty years, I have experienced a lot
of strange happenings with the systems.

A couple of years back, I found myself struggling with a 'home made'
unit that played O-rolls.  It had exactly the same fault!  I pulled off
tubes, played the nipples with my fingers and _everything_ worked
perfectly.  It would reverse, lock, and snap back into play.  One had
to conclude that if everything worked perfectly, then the devise must
be getting a signal!  I traced this back right to the tracker bar!

Was the roll flapping on rewind, enough to let atmosphere enter the
play port?  No!  So now what?

I covered the tracker bar with masking tape, and poked the reverse and
play holes open; and when operated with finger tips, it worked
perfectly.  I put the roll back on.  While laying on the floor -- roll
in place, reverse hole open, latch pneumatic trying to send things back
to play -- I reached up and touched the paper roll.

Mystery solved!  The tracker bar was ever so slightly out of alignment,
allowing just enough atmosphere to enter the release to play valve!

This was a front to back adjustment, not the up and down.  It took only
a half-turn of a mounting screw and all troubles were gone.  The unit
is still playing 100% dependably to-day.

Experience is a great teacher!  Enjoy your now dependable music.

Seasons greetings to all from
Ken Vinen in Stratford, Ontario, Canada.