Can’t say if the motor/transmission is the same across all mirror assemblies.
I just checked my spare flag mirror and there aren’t any part numbers other than a label on the back side - 944.731.027.01 which is the entire assembly.
One thing that can happen is that the gear and corresponding track can jump off usually due to being stuck, manually forced, over extending (common with sunroofs), ice jam, dirt, corrosion, none use, etc.
It’s easy enough to remove the glass and expose the condition of the two (2) motors and gear sets.
Beforehand, I’d try and lightly coax the mirror up/down to see if it’s stuck and maybe you can free it up, might be just dirty or jammed tight.
Also, if removing mirror, it shouldn’t fall out but careful with the attached wires for heat (2 brown), don’t force the glass as it may be a bit stubborn, the rotating lock ring must be fully to the left. Don’t force glass, just try to pry it out at different points.
EDIT: Mirror pictured was not installed and upside down for demonstration photo - therefore the locking ring that releases the glass is located on the bottom as is accessible by tilting glass up to expose the ring and then slide the tab to the Right.
Also, some earlier models instead of locking ring, the mirror glass is held in by four tabs on each corner.
In case you need to remove glass on late 80’s:
