Get more traction by naming specific Performances.

But generally:

[EDIT] a PART,
Select "Common" (lower right),
"Mod/Control" -> "Control Assign" menu,
upper-left touch "Auto Select",
Push the Assign 1 switch,
look at the destinations and determine which one(s) is(are) changing the output level. Could be a gain on an amp simulator or something not clearly labeled as volume. Or turn off Elem SW for all elements.

You could delete destinations one by one too to find.

That"s one way A.SW1 can work. Another way is XA Control which, when on or off, will toggle if an element is sounding or not.

Edit the part as above, but instead of "Common", select an Element (start with Elem 1 and go down the line). Then:

Touch "Osc/Tune" menu,
Look at the "XA Control" parameter
If this is set to an A.SW, then this will toggle the element. You can either turn the element off completely or remove XA Control so the element always sounds.

Here's an article covering both possibilities: https://www.yamahasynth.com/montage-category/assign-switches-1-2

The above was for items if they are NOT the A/D Volume. For A/D Volume, you would:

1) Press [PERFORMANCE] (HOME)
2) Use touchscreen (TS) to touch the Performance title at the top of the screen
3) A menu pops up on the left-hand side. Choose "Edit"
4) Choose menu "Control" -> "Control Assign"
5) TS: Turn on "Auto Select"
Here - your only sources can be the assignable knobs (or superknob) - so A.SW1 should not be able to be used as a source here.

OR - you could try to fix the A/D level by the new FW version 2.0 feature

[UTILITY], then "Effect Switch", then turn "Global A/D" ON. This will prevent the A/D volume from changing when you switch Performances. I'm not sure if it also ignores/overrides offsets applied - but you can see if it does.

Thanks for your reply Jason. I found the reason that my volume changed. The assign 1 knob switched on my overdrive on my Nord keyboard via Midi. Problem solved, thanks.

Thanks for your reply Jason. I found the reason that my volume changed. The assign 1 knob switched on my overdrive on my Nord keyboard via Midi. Problem solved, thanks.

You can prevent such random events by using the Zone Master function built into each Performance. In general, it is a good practice to take control (pun intended) over what gets transmitted Out via MIDI in each Performance you are going to use. The Zone Master function should be used whenever you connect the MONTAGE to an external device via MIDI.

There are a ton of commands that the MONTAGE transmits Out... the primary goal of the items MONTAGE generates is to ensure every move, every nuance of your performing on MONTAGE can be captured and reproduced when that data is transmitted back to the instrument.

The Zone Master function allows you to create a Part slot dedicated to your external device. This way you can control what get transmitted to that external device... this way an AsSw will not change the Overdrive on your external device, ...unless you want it to...