D/S Mirror Dimming Oddly

[Poppy's Denali]

So I've noticed lately on my '06 Denali that only my D/S mirror will dim (Turn a bluish color) when I am in a storm, or dusk/night when a car is behind me (When it really shouldn't (Yes, I understand the feature and when it should kick in, but it does kick in when it shouldn't)). My passengers side does not change. When I first noticed this, I thought the mirror was shot (Had a 99 Jeep GC and the mirror yellowed on me), but within a few minutes, the glass went back to its typical clear self. Again, I only see this on the D/S. It's heated, and the turn signal works fine. The glass changes sporadically every time I drive home from work (Night time, or dusk). New mirror time? FUBAR sensor?

TIA

 

[sumo]

possible. I think the mirror is triggered by the interior rearview mirror, Is there something hanging or blocking the sensor on the Rear view? Passenger side does not dim