Which map is it? Some maps have barriers for armored types so that they have a longer way to the base and thus aren't closest to the base even though they are further from the spawn. May this be the reason or is that not the case on any of the maps you encountered that behaviour on?

No I have definitely also noticed this. When armor dual spawns with anything my snipers will kill all of the other enemies before starting on the armor. They are on the same path and everything. The armor will be in front of the other enemy, both within range, and my sniper that is set to first targeting will kill the other enemy instead of the armor that is in front of it

On the first map I made it so that the armored have a shorter way. They get killed before the strong. On the second, all enemies have the same way. They get killed based on who is nearest to the base. I can only reproduce the issue in a setting where it is the intended behaviour and thus not an issue (like 3.6 or 4.4).

"First" target is the one who will be the first to reach the base. This have already been reported but it is an intended behavior