Faulty reverse lights Mk2 Mondeo ST24 1997?

Hi all. I have a problem with the reversing lights in my Mondeo ST. They will only come on if I pull back hard on the gear stick while reversing. If I let go, the gear stick moves about 1/4 inch but it is enough to break the circuit. I've had a look at the gear stick area but not sure what I'm looking for. Any idea,s Cheers