I ended up scrapping my MK1 Octavia for a similar problem, all 3 passenger doors deadlocked, I am 100% convinced now after owning VCDS that had I had it at the time and would urge the OP to find some way to get it scanned.

 

The door lock microswitch can cause other funnies over and above the courtesy lights etc but if the door is deadlocked you risk damaging components and destroying the lock to replace it with no improvement.

 

I think its likely to be a canbus comm problem between the drivers door controller and the passenger door, possibly a broken cable in the door loop, if the passengers door window switch does not operate the window than it would lean towards the passenger door controller or corrosion of the connector.

 

I think all these things would be revealed by VCDS, it really was the best investment that I have ever made,with it  I would never have scrapped the previous car, given how much dealers charge for a daignostic check which is only as good as the person doing it and the long distance from you to the dealers I would get one.

Did you ever manage to get to the bottom of your problem.

 

I have exactly the same intermittent problem with my n/s door, window and mirror.