When actor billboards are very far from the camera they will begin to flicker. They flicker in our shooter game project as well so the distances aren't so extreme that they are unreasonable.
The billboard will noticeably flicker in the viewport where it touches the floor.
The billboard either doesn't flicker or stops rendering due to extreme distance
NOTE flickering occurs in shooter game example project with sphere reflection capture billboards
Head over to the existingAnswerHub thread and let us know what's up.