2003 defender 110 doors

Hope someone can help me.
I am having problems with my 110 defender doors. When closing them they dont close properly and only engages the the safety lock on the door to prevent it from opening on its own. To close the door from this point the only way to close the door properly is from the outside and to achieve this you have to push hard and quickly next to the door handle (marked in red on attachment) and even when doing this you might have to do it a couple of times.
Any comments are appreciated!
Cheers

Could be that the hinges have worn and the door has dropped a little, when the drivers door is fully open, hold the bottom left corner of the door and try lifting up and down. There might be some play in the hinges meaning they need replacing.

Or the door striker on the B-post might need moving slightly so that it aligns with the door lock as they meet.

Mine does the same but only when its really cold.

The plastic tube on the striker might have split and is buffering the door when it's shutting. If the tube has split you have to buy the whole striker assembly. You can however tape it up as a temporary repair while waiting for a new striker.

The other thing that can happen is that the door card could be coming adrift from the door and again causing buffering. I have this issue on one of my rear doors at the moment.