When I set mine up like yours, and use _ToggleLeftSidebar assigned to my left screen edge, I’m getting the same menu each time.
So far, I’m not able to duplicate what you’re seeing.
In RhinoWIP > Preferences > Commands, I assume you’re using a copy of the default command set.
Did you by chance add a new Palette duplicating the “Main” name of the primary Main palette?
It looks like you may have.
I see Main+Standard in your primary list, and Standard in your modified list.
When I tested it last week, I created a palette with a duplicate name of another with different icons in it.
I could not get it to act like you described.