I have a E34 1994 525iSE. When I put the gear into reverse, I get an error like LIC PLATE WARNING message. Got somebody to check out the reverse lights and they are not working when in gear and the licence plate lights switch off. Take it out of gear and the LIC plates lights works again when the lights are on.. The same problem happens when I switch on the rear fog lights.

Any clues on what can be wrong.