Thanks George.
If I understand you correctly, Van Basco is fine, doing what it is supposed to do, but my MX100A is just not paying attention to the "note off" or sysex commands. So there are no settings anywhere to resolve this when using the VB software.
Fair enough, I'll just be careful about how I use it. VB is very easy and convenient when I just need simple playback of a MIDI file so I'll work around the problem. It's mostly for testing purposes that I need to stop playback in the middle of a file, so I guess it is not such a big deal. I'll also try the Disclavier power-down method and see how that works.
Thanks for the info.