Here is an odd one. 60mph on the way home, someone pulls out of a junction causing me to brake down to about 30mph fairly rapidly. Pulled the main beam lever as I am slowing to 'let them know I am there', nothing, no change, except disabling the auto main beam. Finally get past said car, open road, 60mph, pull the main beam..... repeat experience. I get to the next village, slow down to 30mph, pull the main beam - worked perfectly.
Differences were purely speed and a lit/unlit road, is this another 'safety' feature. Auto Main beam works fine on the unlit road and goes back to normal lighting on lit road - which makes sense.