This one is occasionally extremely frustrating.
if anyone cares, i have a map on my file share that i created.
This will take you to the skull directly through a teleporter, just hold down x while walking through.
or follow video guides and build your own path there.
Edit: People seem to not know how to get the skull, near red base you will see a path leading out of the map, infront of the path i placed a teleporter. Walk through the teleporter and quickly hold X to pickup the skull.
Edit2: Included a youtube video on it