I have had a similar problem, don't know if it will be the same result though.

On my vehicle it was the tailgate opening and lock switches above the rear number plate full of water. Suggest you remove tailgate inner panel and leave off (so you can open boot from inside afterwards), disconnect both switches and then see if it is ok. When I tested mine with ohm meter I could see it was not going from zero to infinity cleanly, when connected current was flowing very slightly but occasionally flowing just as nuch as when the switch was being operated.

Graham