He probably was conflicted about what to shoot at. Giving to many orders can also cause issues. Last probably did not have precise LOS to tank. If infantry where around as well as the tank, and I am guessing yes. DO THIS.... Click the icon that selects only target tanks. AND set a fire arc on the direction of the vehicle is in. It is much more likely to engage the target you want. But in the end its up the unit what it feels is the greatest danger. Sometimes it picks the wrong thing. But then, so do soldiers.
Thanks i will try it! The battle was in forest area and it seems the tanks and vehicles behave quite strange in these areas. In open space, they usualy pick the prioity targets quick. However in forest it seems like the AI is very confused of the environment and maneuvering in it.