Tail Light problems of the 1999 Oldsmobile Silhouette

The contact owns a 1999 Oldsmobile Silhouette. The tail lights malfunctioned. Has two vehicles manufactured by gm , the other vehicle is a 1999 pontiac montana. The tail lights failed and will not work anymore. She has to turn the emergency lights on to let people know when she trying to stop. She has heard about several other 1999 -2000 models that have similar problems with the tail light assembly. These vehicles are used as taxi vehicles . They have to be right because they are hauling passengers. The pontiac was purchased two years ago, and it has been doing this for the last six months. The Oldsmobile was purchased four months ago and tail lights malfunctioned since purchasing it.