Ive noticed that sometimes if you're not auto locked onto a target and trying to manually aim, the targeting system will start pulling towards a tank in the area even if you're tryimg to target another tank. I was using zoom and sniping a tank when another tank drove by behind it and my cross hairs began being pulled, on their own. following the moving tank against the direction i was going in. And I'm not the only one, at least two other players mentioned this happening to them as well.
#Cross Hairs/targeting moving on it's own
fallow nimbus
lime mist
there's an aim assist setting, it's probably that