Hi, the lock mechanism can and does also fail and need replacing. This happened to me at the start of a remote trip - was replaced under warranty at the time. Don't know what the failure mode is though, it's been fine since with the cleaning regime noted above.
I also found that if the door is pulled in overly tightly on the adjustment it can fail to open - hence Slunnies method of pushing on the door when opening works.
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1996 D1 V8 - gone
2002 D2 Td5 ES- gone but still running elsewhere
2013 D4 SDV6 HSE - gone
2023 Defender 110SE D300
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