When watching the replay from my last game, I noticed that Avengers which are on patrol don't appear to shoot an enemies. This was late game where I had one planet under my control, and I had placed some orbitals to produce Avengers that would patrol the whole planet. When my enemy sent a group of Avengers on my planet, my patrolling Avengers did not shoot at them - they just continued their patrol route even when they moved right next to the enemy Avengers. However the enemy Avengers did eventually get all killed, so maybe the patrollers *did* shoot them, but there was no animation showing that. (BTW, Avengers are really bad at hitting moving targets.) Is this a known bug?
That does seem to be the case. On patrol, regardless of their maneuver setting, orbital fighters will only shoot things that happen to pass vaguely in front of them. They will not stop or turn to attack.