Hello, I have an issue. I have been working on a tower defense, and along the way my Turrets have stopped working properly. When I build a turret they will not attack enemies in range until I select their first target. After I force them to attack their first target they are fine and will attack the next wave without a problem and will continue working properly until I upgrade them into a new turret. It's just the first time when I place or upgrade the turret to a new turret. Anybody out there know what I messed up?