This is not normal, but is not too unusual either. If the lock etc in that door malfunctioned at sometime in the past, it may have been replaced by one that does not match the drivers door/ignition. Have two cars this way myself. You just need the key for that lock, or replace with one matching the drivers door from the dealer.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150