But to add something new that previous comments haven't:
(1) there is a button you can push to auto-snap between enemies. On PC with DS4 controller, I believe it is L1. (2) using grenadier units armed with anti-personnel ammo, isn't going to be effective against tanks and armored units (3) "???" typically means the unit is guarded (i..e. crouching) or your bullets are ineffective against that enemy type.
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