Unfortunately, there are no mechanical switches inside in the door lock mechanisms - they are all hall-effect sensors (a type of magnetic switch), so no amount of spray lube or cleaner will change their operation.

Either the lock mechanism is not actually closing properly (in which case some cleaning/lube spray may help*) or the sensor is faulty, probably requiring replacement of the entire lock mechanism.

One other possibly is a wiring fault or a fault in the driver's door switch module, which acts as a controller for both front doors. Maybe check for water damage on this module?

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Wayne
2005 BMW X5 3.0d (b 02/05)
2001 BMW F650GS Dakar (b 06/01)