The driver's door on my VW Golf mk4 is not closing from time to time specially when it's specially cold. The door opens just fine, but then I'm not able to close it unless I reposition the hook on the closing mechanism on the door, so it can catch the metal ring on the door's frame and the door closes. Until do that door isn't closing and just bounces back. You can see an image of the hook I'm taking about below.
I applied some WD-40 also to try to make to move things along, but I don't know if it's a solution that it's going to last.
I would bet that the main problem is dirtiness. Old grease and dust mixed that with the cold gets really hard and keep the mechanism from working properly. I'm thinking to use a brush and gas —lighter fluid— that have helped me to clean this kind of thing in the past quite well.
On the rear passenger door seems that problem is the opposite one. The door is not opening and not until I open an closes a couple of times the door not open. This door didn't lock in the past in some occasion and the problem seemed to be fixed after a applied oil.
Are my door locks mechanism just dirty and acting up just because the cold weather or these things can be broken since the car is almost 15 years old?