I am getting an intermittent warning on the dash to say that the drivers side brake light is out. SWMBO has followed me in her car and said that the light is out when the dash warning displays. However, at other times the light isn't out and I don't have the dash warning. I checked the bulb and it is fine, but I replaced it anyway just in case. The bulb holder and the wiring from the bulb holder to the car body are fine. I suspected water ingress as in the past someone has damaged the two rubber retainers that hold the rear light assembly in place so that it is not held snugly in. But, I have checked the assembly over thoroughly and there is no sige of any damage or of any water. Any ideas?