I know that these posts are old, but they showed up in my search. I was having the same missing landscape problem around Gallows Rock. The only thing in my search that helped was another post saying they had to reinstall the game itself. It gave me the idea that maybe my base game files were messed up. I switched to another profile loadout( for problem solving mods), and only activated LAL and USSEP. The landscape was still messed up, which helped validate that it wasn't a mod conflict. I didnt reinstall my enitre game, though. I just had Steam validate my game files (it said two files had failed and just updated those). I went back into my game and the landscape was fixed. I am not sure what caused it. I can only think that when I updated the game earlier that it did not properly update and my files got messed up. I hope that this helps someone else in the future that has this same problem randomly show up.
