Hello,
Had the same problem with my 5 door. Switch would lower the rear window but the rear door would not release, almost felt like it was locked.
Mine still had warranty on it so went back to the dealer, turned out to be a faulty lock mechanism, which they replaced.
FYI, I had problems getting the rear door to catch when you closed it for a few weeks before it finally failed, not sure if you have had the same issues?
Cheers
Jamie