If you press [+] (and add anything) on Part 9 this should disable SSS. The SSS emblem should go away. There are other ways - but the reason why I say Part 9 is so when you're playing the keyboard (and Part 9 isn't selected -- which isn't a likely situation) then Part 9 will not engage and will ignore the keyboard presses. I know you're controlling this with an external device - but this suggestion, I believe, is the "cleanest" overall.

If I were faced with this, I would want to check the MIDI data to be sure all Note ON events have a corresponding Note OFF event.

or you could lift all your fingers off the keys (and release sustain pedal if depressed) before you send the scene/program change from the Akai, which should assure the Akai is sending Note Off to each played note of the old Yamaha sound before switching to the new.

A stuck note is very different from the SSS feature. One is a data error the other is a feature.
It is likely your stuck note is due to some (faulty) data — look to make some kind of MIDI data correction.

SSS would have all notes that are engaged to hold; as long as the data sent continues (all notes would hold, sounding the initial program)… when the documented Note durations have ended, the SSS held notes would end.

You describe your issue as a ‘stuck note’ - one that rings out without stopping. That certainly does not sound like SSS, to me. SSS does not hold without stopping, it stops according to your controlling Note data (not on its own or by being, or behaving, ‘stuck’).

I would start exploring the events you are asking to be reproduced — likely you have your Program Change (or Changes) stepping on the hem of the dress of your last note entry… sending a Bank Select and Program Change without awareness of what notes are asked to be held could cause this… or just plain sloppy event durations that could extend over the measure line (or the positioning musically of your Change event).

Things like Motion Sequences or SmartMorphing movement can also cause unexpected results, when used without care but you do not mention that you are using these features.

Start by looking for Note-ons that would cause the duration to extend over your measure line the has the BankSelect/ProgramChange event. Look for notes that cause hang-over, look for notes that come too early (like just before the measure line that would cause it extend into the measure containing the Change). It likely sloppy data placement… the behavior of the SSS feature is unlikely to cause a stuck note.

You give NO INFORMATION on the specific Bank Select and Program Change that you are sending, no mention on which MIDI Channel on which you are attempting to address your MONTAGE, no mention of the MIDI I/O Mode setting on your MODX/MODX+, no mention even of how many Parts the MODX/MODX+ Performance contains (both in the pre-Change and post-Change Performances), no mention of Sustain pedal usage… etc., etc., etc., let us know, at least some of these things, if it still remains a mystery.

Hope that helps.

If I were faced with this, I would want to check the MIDI data to be sure all Note ON events have a corresponding Note OFF event.

I mentioned this because my suspect is that the program change is sent while Note ON messages are outstanding without a corresponding Note OFF. And, after the program change the Akai doesn't send Note OFF messages for the outstanding notes.

This is obviously not an issue with SSS although if you did disable SSS - you could mask the problem with the bad MIDI stream because notes would be cut off. This is why I didn't make any argument to your general approach. If disabling SSS (which I assume you don't need to utilize) "fixes" a MIDI controller problem, then that's probably enough to get you past this.

Even if disabling SSS masks the problem - this doesn't mean SSS is faulty.

Akai Force (and MPC) has had a laundry list of MIDI bugs. Firmware releases are steadily improving things and users generally find work arounds to the bugs to deal with something invalid the Force/MPC does.

A much dirtier trick is to jump from one SSS Performance to another, and then to one more. This disables/mutes/kills hanging notes, too.