Hmm. The drivers side rear door (pin) is playing up. Once locked it doesnt come back up and open when all the rest do. Very frustrating. The other day it didnt lock, left it all day in blackpool. Lucky nobody saw it and robbed my headunit!

The lock actuator failing is a common fault. change it before it fails when locked

 

http://www.pimpmyskoda.co.uk/Doorlock.htm

I have fixed two of my doors by lubricating the mechanisms. I sprayed a combination of lubricants 1) from the outside through the gaps around the lock on the rear edge of the open door and 2) took off the door card and lubricated the lock mechanism with similar sprays from inside. 

 

I found it was friction in the lock that prevented the tell-tale pin from coming up. It is a couple of years now since doing this and all is still working. Worth giving it a try before putting in a new lock at great expense.

 

Incidentally, when things first started to go wrong I found the pin would come up or down if the remote push-button was operated twice, once to start the lock moving a second kick to complete the job.

 

The lubricants I used were a teflon/oil spray used by VW garages followed by a silicone oil spray.

Check the wiring between the door and B-pillar inside the rubber tube