Tailgate lock problem.

My brother has a '00 330T. Sadly he lives a long way off, so I'm hoping someone here has some ideas of things to check.
The central locking for the upper part of the tailgate (window) operates
at random, and opens it. Sometimes with the car on the move - sometimes when parked up.
Any guesses? He says he never uses this facility - but always opens both. And wondered if just disconnecting the motor would stop this but allow him to open the entire thing.
He has only one remote - the other one was lost by the previous owner.
And says there are no electrical push buttons to operate this lock in the car - unlike my E39 which has a button by the driver's door to unlock the trunk lid.
*I'm out of my mind, but feel free to leave a message.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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