Fix Disappearing Units vs AI

This might be kinda minor issue, but it concern and annoys me. The disappearance of units of your enemy AI country is real. Like this scenario happens in a blink of an eye while moving, bombarded, and idling. There is no stealth involves in this situation, literally disappear when I check back a while ago like few minutes. Hope this won't happen against players, and hope I'm not the only one who experiencing this disappearing units. Hope devs do something about this.