Loose connection, or the bulb holder connection is loosew / faulty. I had this with my MW, and in the end i took the bumper down, took out the bulb and connector and made damn sure it was tight with some good old, cure anything Insulation tape, and then, Roberts your mothers brother, it hasn't fluffed up since.
To be honest, the indicator / light system on teh can bus is about the easiest part of all, in terms of the Stilo electrical system, but you have mised an important bit of info matey, When it starts going clickety click, doe the warnign on the dash come on "Bulb Failure" etc.
Let us know, my money (Or ratehr the money i'll steal out of Scotties French maids outfit when he';s not looking!) is on a loose connection to the bulb or the multiplug behind the unit.