Encountered a strange bug with tanks. Apparently, they have no rear... only a front. And it's impossible to hit the real directly.
I've attached a save with two tanks - if you hit them from behind, there's a random (50/50?) to either hit the front or side, regardless of your position.
In the pic attached, the gal stood behind and to the left of the tank, shredding some of its armor with a vibro axe. While hitting every attack, she only damaged the right and front armor.
The expected behavior is to hit only the back armor, and possibly the left (though at this angle, seems like it shouldn't be the case).