where did you purchase them from? eBay or a respected place with only OEM parts?
btw, i think the light comes on if the sensor doesn't get the exact current or voltage reading or something. my mom was having a problem with her taillights in her E39, but it was because she replaced the taillight bulbs with shitty bulbs and it was causing a flux in the circuit.
that might not help, but hey, i tried.