Classic problem of bad lock actuator.
This has been discussed multiple times in E39 forum.

Your best bet: keep trying with the remote for many days. If you are lucky, one of these days, the actuator will work for the last time. If that happens, do NOT lock the door again.
Instead, use that opportunity to remove the trim panel from the door first!

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1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT