I think I have seen this bug in legacy already, with spahis. Melee units with area of effect sometimes just refuse to damage their target, only surrounding units. It’s probably due to some cap regarding how many units can be damaged by the area of effect.
In this clip you can clearly see me clicking 2 doppels to attack a 6 hp settler. That settler never died. It’s pretty frustrating not to be able to control your units properly.