General Cancel re-programmed mysteriously

Hauptwerk Advanced
Hereford Cathedral complete sample set
Four-manual console from Classic

The above organ belongs to an organ student of mine. Yesterday when at his house, I noticed that General Cancel (Hauptwerk's, not the organ sample set's) has somehow been reprogrammed to call up a registration when it is pressed. Specifically a couple of pedal stops, and a 4' Flute on the Choir. I right-clicked on the General Cancel in the floating registration palette and selected "clear all triggers" and attempted to re-program the General Cancel to its piston, but to no avail.

The same behavior occurs when tapping General Cancel on the touch screen as well as when pressing the organ's physical GC piston. I also tried mapping GC to a different piston that had been previously unused, and it also occurs.

I can't find anything in the HW manual about how this sort of thing could happen, and my student doesn't know how it happened, either. How can we get GC to truly cancel everything again?

Thanks!

How can we get GC to truly cancel everything again?

One way which is sure to work is... NOT to use the General Cancel at all! Instead, use a General Combination which simply has everything turned off. (Which you could presumably get when first loading the Organ, or by using the "General Cancel" belonging to the Sample Set). Now whenever you use that newly-defined "General Combination" (via Piston or whatever), everything turns off just as desired. (If some features are SUPPOSED to be left ON with General Cancel, (such as Blower or Ventils on certain Organs) then just be sure that they are ON when defining that new General Combination.

Another way which works for certain aspects with certain Sample Sets... get everything the way you want (everything OFF except maybe Blower and Ventils or whatever), Then using the Menu for "Engine", and the Tab for "Advanced Use", and select "Stop Audio & MIDI". After this, do the same and select "Start Audio & MIDI". On certain Sample Sets, for certain aspects, this will actually reprogram the contents of Hauptwerk's General Cancel to match that most recent configuration. Good to be aware of this "undocumented feature", in any case.

Four-manual console from Classic

For these Keyboards, please note that you CANNOT program a General Combination to the right-most Piston by way of a Setter Piston in the left-most position.. because this action triggers instead a Keyboard "Hot Reset".

To program a General Combination to a right-most Piston (eg to function instead of a "General Cancel"), you have to use the "Setter" Button on the Hauptwerk Registration Pop-Up instead. Then everything should go smoothly.