Auto Dimming Rear View Mirror

[Odd Job]

Hi all,

I wonder if anyone has experienced this regarding the auto dimming rear view mirror.
This is the first car I've owned with one, and I'm not sure if I've got a problem, or if this is what they do!
I've not not driven it much at night, but on Friday I was.

Basically, does it work. YES. It works.
Does it work all the time, or rather when I need it to work. NO

I've noticed that a car with "standard" non dazzling headlights will cause it to darken.
But, I've noticed that if a vehicle has these more modern "turn the road into daylight" headlights, the damn thing wont operate!

I have a theory, I may be well off the mark, but it goes like this.
The mirror shouldn't darken in actual daylight.
So, if the car behind headlights have a beam which is in the daylight spectrum, it fools the sensor and so wont darken.
Does this sound possible?

Many thanks for any ideas and help!