doors not locking

Hi guys, I have encountered a weird issue. The rear driver door doesn’t lock. I noticed when I click the LOCK button it keeps flashing as if there is an open door or an unlocked one. All doors and the boot are locked but the rear driver one. The lock button inside doesn’t work and the key...

I have a 62 plate ce'ed. Lately when I remove the keys from ignition the radio stays on and the doors remain locked for few minutes. Tonight though the doors will not lock unless using the lock button on the inside of tge car with the engine running. I have tried with the key and nothing...