Both wing mirrors respond to movement setting in all required directions from the centre console.
Ever since I got the old bus it has exhibited the following fault:
When selecting reverse BOTH mirrors dip to assist in reversing maneuvers.
After finishing the reverse motion and selecting a forward gear ONLY the Passenger side mirror returns to the normal driving position, the drivers side mirror remains dipped for reversing.
I can't fathom this out. Clearly all motors are working and setting a position for driving/reversing does work perfectly on the passenger-side mirror.

Has anyone come across this little foible before?

Yes. Very common. Wish I could remember the fix. I think they just disable the dipping function but cannot remember how.

@Saint.V8 will know!

Not returning is super common....best to disable the function....