Had the vehicle and the problem for 2 months.
I suspect your thoughts on the cause must be the case.
After it rained for about one hour I went out with a torch and look for beads of water. About two weeks ago drips were appearing at the inside top falling on the plastic trim and running towards the door bottom seal. Striking plate adjusted as there was about 5mm of door movement after it engaged with the lock. Water then stopped dripping from the top, but is still collecting inside at the bottom.
I need it to rain again and go out with the torch, but not until after I have renewed the rear door lock as that door is now failing to unlock
Lock now removed and door held shut with a bungy
![Sad :(](./images/smilies/icon_sad.gif)