Having read all this I am certain that it is, by default, what Scott did not save that caused the changes to occur.
If you don't save sound to panel memories then that area - sound - will be open/subject to every subsequent deliberate or accidental change that occurs sound wise whether it's Right 1 Right 2 or even Left.
I can understand Scott finding a method to ensure continuity of play particularly if the music is uptempo and Scott is singing to it - hence the use of SD Song Medley. What I guess he's never discovered is just how quickly SD Cards load the next setting for the next number with all the safety factors built into that approach for saving/recalling your work.
Incidentally I move custom styles as quickly as possible to Memory bank 'A' as Custom Style is liable to be altered by adding other custom styles!!!