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Sounds like you are having a problem with the driver door module which controls the remote locking system. If the problem happens again use the key to get into the vehicle and see if the doors will lock using the door handle on both front doors. If this will not work from the driver but works from the passenger then I suspect a faulty driver door module or door latch.
If the lights flashed then the module received the rf signal and sent the signal to the fem and rem to activate the lights but either did not operate the door latch or the latch itself is faulty. When the problem happens you can disconnect the negative battery cable for 10 minutes which may reset the module just make sure that you have the radio code.
Sounds like the driver rear door latch will need to be replaced but it may not be the only issue.
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