looks like the F117 aeroplane model is something wrong, this is large sized model stuff/object, but when i was in the map editor, after i put that down onto the land of my map, i have to keep pretty close(short distance) to that model, otherwise, the whole airplane model would suddenly disappear, but the coordinate for the object model is still there working... i think , maybe the L.O.D. setup of that stuff is something wrong?? or you once wrongly resized that stuff, or what... i don't know, i am not a model creator...

multiplayer servers have a bug where players can move through constructions