2006 Vauxhall Zafira driver side back door jammed shut

All I can suggest is what I've done in the past,
two man job with one operating the outside door handle while the other laying on the back seats basically "kicks" the inner door panel.
You can cover the door card but damage is normal.
It's brutal but might work.

I had this on mine, the garage told me the fix would mean ripping off the door panel as it's so fiddily, they advised it was more than likely a damaged wire relating to the central locking.
As there was so much else wrong with it, emission light was on dash for 3rd time indicating some sensor needed replacing, I forget what it was called, springs on suspension, passenger door window wouldn't go up, AC stopped working and the list goes on... all within the space of a week plus the resistor problem and my MOT was due (55 plate but looked after and low mileage) decided to cut my losses and get a loan out for new car, I sold my car on obviously advising of all faults, I got 2012 Meriva...the power steering just failed on that so I'm having a bad car year!!!!!