Disco 3 (LR3) Passenger side memory mirror with mind of it's own !!

Hi again Guys...Since owning the car, I have had intermittent niggly problem with the passenger side exterior mirror moving out of position when the ignition was switched on. Sometimes it would move itself upwards to the maximum and other times move down to the maximum . Retaught the memory and it could be fine for a few days then decide to go crazy again, usually after rain or after washing the car. When revers dip was enabled, it would never go to the preset position more than 2 or 3 times so I switched the function off.
Whilst I was carrying out the autobox and transmission servicing (See my post on that one) I decided to get a new mirror motor and fit it. The electrical connection to the motor is good, with no signs of corrosion etc.
My first impressions are that it has solved the problem and for the first time the mirror responds to the two memory settings (Keys 1 & 2) in both normal and reverse dip mode
Early days I know but I think it's sorted. The heavy rain we have forecast for tomorrow could well be the proof.
It was a quick job to do, took about 20 mins. from start to finish.

UPDATE....
After just over a week of everything working fine, it's started playing up again
Yesterday instead of dipping to the preset setting in Reverse Dip mode it decided to move upwards towards the sky !! Retaught and stored the new setting and later when I selected reverse it lowered to it's maximum position.
I have a new memory module which covers the seats, steering wheel and mirror settings but I need to enter the barcode for the steering column into it.
So it's disable the reverse dip function and back to square one until the module is fitted and programmed.
I can live with that