A few more observations:

The change from Env Mix = off to Env Mix = -100 occurred to both programs and presets.  I manually set these to Env Mix = 0 and saved them with no troubles.

I did have 1 program and 2 presets in which Env Mix did not = -100 today.  When I checked these today,  Env Mix = 0.   No correction needed.

I don’t know for sure but I suspect that my “-100 changes” were limited to programs/presets in which Env Mix was previously set to “off”.  Restated, I suspect that when I programed Env Mix = 0, things stayed that way.

Hope that helps.