I tested UT800 front light for the first time on descent through dark tunnels. I had Auto Beam Adjustment set to On and it got me into a dangerous situation twice.
Light was set to High intensity. As I approached the first tunnel I reduced speed and just before entering the tunnel, the light switched to Low. My eyes were adjusted to daylight, there was no light in the tunnel and I was effectively blind.
At second tunnel I intentionally did not brake, so that light would stay on High setting. Another mistake. In front of me was another rider with Varia radar, and since I was approching fast, his light flashed bright (as it should), and my front light went to Low again - this time I presume because of bright flash in front of me. So I was blinded in the second tunnel again.
That makes me think - if at night a car approaches, does Varia light go to low because of car's bright lights? If a pedestrian steps on the road in front of you and you brake, does the light go to Low becuse of reduced speed?
Reminds me of Danger Goggles in Hichhiker's Guide To The Galaxy. In case of danger they blind you, so you don't see the danger. Varia front light does the same.
This kind of behaviour is very dangerous and I would advise to turn Auto Beam Adjustment off until Garmin fixes this.