I have found out how to do it very well. We have successfully went in from the Grottos to the Forgotten Shore without it actually loading for many times. So I'm going to start from the beginning. Make your way to orbit. If you haven't already made or joined a fireteam with your friend(s) do so now. Once you are ready make your way to the Strike, Devil's Lair. Once in do not follow the Strike path but make your way to the Steppes. Once there head to the Forgotten Shore than a little more farther into the Grottos. At the far end of the road there would be a turn in the Grottos, do not turn instead drive off the road into the water. That water and the water around it is drivable. Now once you are on the water drive towards the Forgotten Shore. Don't drive to far out to the right or your sparrow will tumble around. Head for the small incline in the Forgotten Shore, now here's where many people fail. Before you go up that small incline drive to the right of it then curve in. I would suggest to not boost until you find where this invisible boundary is. Once you have successfully made it into the Forgotten Shore without it actually loading walk forward and you'll fall into a patch of ground and be under the map. Walk around until the Forgotten Shore loads and you are still under the map. I usually head for that rock near the edge of the water. Once loaded head for the structure that the fallen have made their home. There should be a square platform, oh and if you didn't get it already there should be a dead ghost there, jump on that platform and wait for the map Bunker RS to load. Once loaded you will be in a glitchy place, There would be a weird diamond shape in front of you. Crotch and walk to get in it. Now once under make your way to the garbage pile, now things get a bit too hard to explain instead I'm going to link a video about people doing it, it's in the spoiler.[spoiler]https://www.youtube.com/watch?v=RZmxNjRcI9Y[/spoiler]Once you make it to the end you let your friends leave the fireteam if you are leader, or you leave if you are not and join back in. Once you do that you or your friends passes on the fireteam leadership then he/she/you leave and join back. Now you 2/3 will be inside. Feel free to explore and if you want to get out just head back to orbit.