Polo Central locking problem

[ccarmock]

I have an 07 Polo 9N3 that has started to suffer a problem with the rear passenger side door. Intermittently it will fail to unlock. When it does that the button on the door remains down and the door is deadlocked as it cannot be opened from the inside.

It will occasionally also fail to lock.

When this happens I can't hear any noise from the mechanism in that one door. Usually locking and unlocking will make it work.

I took it to VW who said they couldn't make it fail for ages and then it did once. They suggested they could replace the lock mechanism in the door at £320 inc fitting. In reality they advised me to wait to see if it gets worse as it will be easier for them to diagnose if it consistently fails, since they can't be 100% sure it is the lock mechanism. They were very good didn't charge me for the diags. They said there are no reported errors on the ECU.

So all in all good service from VW who didn't just start replacing parts and charging me.

Anyway I have read that this fault can be due to dry solder joints or a failed locking mechanism.

Given it is intermittent, and when it doesn't work, there is no noise from the door at all, I am thinking maybe dry joints? made worse by the damp weather?

If so, I am good with a soldering iron so happy to have a go at fixing, but would welcome the view of others before I start.....