Update 3: New project did the same - same result. STill rubberbanding
But when placing a ramp in edit mode and starting the game with the ramp still beiing there it did not rubberband. I have the suspicion this occours only on worlds that do not use any props / bulidings on the on the normal fortnite grid and only use build to prop. My current suspicion is if you do not have at least 1 structure on the structural grid it will create it at runtime causing huge lag