I have cleared all the stealth killable enemies in the Camp of the Horned Devil, hacked the robot, and am have snuck back out of the of the camp and I am attempting to finish the enemies.
I am doing this by positioning my team behind the trees across from the bridge with the tank enemy. Then I sneak up with Dux and start the ambush run him back behind the tree and using a controller I scroll through my options 50% chance to hit, too far for a grenade but then I get to the Knee Shot and it says “No Enemies in Range” weird but ok I go back to make an attack and now it says the same thing. I can switch characters to get it back but you can’t do that in every situation.
So in short it seems that if attack from far enough away the game only allows to you target them once and if you don’t take the shot (not ability, regular shot) you are Out of Luck.