The drivers door module controls all the other doors, when water gets in to it it can do all sorts of funny things. On mine the left rear door would not lock / unlock, they would ping straight open when using the remote and would sometimes lock / unlock themselves when driving along. hanged the drivers door unit and it sorted it. I'm not saying this is definately the part that has failed on yours but the symptoms sound like it and as said, it's a common failure on the mondeo!

This is the part you will need.

http://www.ebay.co.uk/itm/FORD-MONDE...item5ae9959abb