If anybody cares anymore: I had this issue with a fresh game, no Mods installed. Then i searched and found. I use the command "tpc" in my sStartingConsoleCommand Line (in the fallout4.ini). It toggles Preculling to off. When i'm standing right before the Elevator and toggle tpc in the console i can see it hiding (tpc=on) and reemerging (tpc=off). Tested it also with "bPreCulledObjectsEnabled=0" set in the Fallout4.ini. Same result. It does not happen however with any of the Preculling Mods to be found here on the Nexus. I begin to wonder which other Objects in the Gameworld might disappear because of that Command? Anyway, since i find the tpc Command Method more convenient than a Preculling Mod (no extra Mod installed for that reason, some Waterboarders go crazy, not working everywhere, always has to be last in Loadorder) i stay with the Command. By the Way, is there also a Command which can be used instead of "bUseCombinedObjects=0"?