Third Brake light is not working !

[Golf-Sam]

Hi guys .. just found out that my third brake light is not working .. i looked at the bulbs .. they seem to be fine , the rear light cluster's ground wire is a bit dodgy .. it comes loose some times and the whole cluster goes crazy . . now i made sure that it's secure .. but still my third brake light doesnt work .. it only comes on when i take the ground wire off .. any one had anything similar happen to them ?? im really confused here .. would appreciate any suggestions ..

[badgerboards]

tried the fuse? it had me stumped when i had that problem till i remembered the ole fuses

[Golf-Sam]

i checked the Brake light fuse .. No 20 .. it was fine .. *pulling my Hair*