locking/ unlocking drivers door

have a 2005 transit duetto , recently locked my drivers door with key and yellow flash light comes on , not all the time , occasionally .then later go to unlock door with key ,wont open have to use remote button instead , is this normal or does lock need oiling . if flash only comes on sometimes why not all the time .always use key to lock/unlock door as only have 1 remote , any answers please , what if remote doesn't work how do I get in the vehicle .
many thanks , any one else had same problem .

hi again , I find it surprising that no one else has had problems unlocking/locking the drivers door , without key entry and remote button failing how do you get in the vehicle .help !!!
mike