Passenger's door latch problem

Since a couple of weeks, sometimes I am unable to open the passenger's door from outside of my E46 (2004 330d). After pressing the unlock
button of the key, for some reason the passenger's door latch mechanism became half engaged. It looks the mechanism fails to release completely the latch. It started to fail after three weeks without using the car. Anybody else had this problem? Any idea why? Thanks in advance.
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