Hi Roger I hope you're well. Things are c4azy-busy here as usual lol.

Many midi files fade out by controlling the master volume or set the master volume to zero at the end of the track for another reason. They should re-set the master volume subsequently but often they don't. This could be it try step editing the last bar of your control track and add a command to reset the master volume.

Hope that helps.
Kind regards,
Mike