I recently unlocked the guided missile for tanks. The first round using it was a blast. I ended up killing a total of 36 helicopters, tanks and vehicles.
However the second round (and every round since), was terrible. The little lock-on symbol that previously appeared when I pointed at a vehicle, doesn't show anymore. Which means I can't fire.
So I'm puzzled as to why it worked brilliantly that first round, but hasn't worked since.
Am I missing something?