Heres a reply from some other forum:

Bartek its something to do with the deadlock mechanism. The passenger door doesnt open with the remote or from the inside but when you physically unlock it with the key it comes open. The back doors not having key holes are unable to be manually opened.

When we looked in the manual it says about the second phase deadlocking. Apparently you push the open button once and the drivers door and boot unlock, which they do. then push it again within 3 seconds and the rest of the doors will open - that is as far as i can work out the only bit thats going wrong.

It says you can deactivate the deadlocking by doing a sequence of key turns in the drivers door but nothing worked when me and eddie tried it.

Options: ford/mondeo owners forum, ask some questions or garage!