[room217au]

oh, ok.  The material for the side mirror is a separate material to the others.
Any files in any folder with the name ‘share’, exist in the game already. All trucks use those files, even SCS trucks.
I always remove those files from RTA (and other) trucks because they overwrite the game files of the same name, at runtime.
The reflection from those mirrors though, is quite a different look than the others.