Car door lock/unlock jammed

I have a Honda Mobilio model car. On a fine day, I see that the manual central locking of the car from the driver side seat is kind of stuck. I say, its very very tight. But using the remote, this along with the other doors work properly. Manually all the other doors are working very properly. When I try the same driver side door from outside using a key, its still tight. From inside, its almost impossible to manually lock the door. What can be the possible cause?

Bad door latch assembly, or one that needs lubrication. It might be the door lock actuator itself that is failing. The door panel needs to come off so the actual problem identified.

Thanks for the quick revert to my query.

I did show the same to a local garage mechanic and he did the lubrication part. But still it didnt help. If its the door lock actuator problem, what can be the solution? Why then is it working properly with the remote key?