Simplest way to reproduce in a controlled environment:
* Open editor
* Place player as flying AH-6 over one end of the airport runway
* Place one or more rabbits at the other end of the runway
* Enter the mission, point the chopper at the area of the rabbit(s) and right-click to zoom/target
At a distance it will register as 'unknown' and then be revealed as a rabbit once you close in.