This could be a long shot, but in editor go to Build and Build Landscape (throws out a lot of warnings, errors & stuff not just landscape) , then in the window that pops up down the bottom is show, unselect the yellow warnings and see if there are any red errors there, that may point to a potential cause.
If it doesn’t show anything, and if no one posts with a better suggestion, is to copy anything in outliner that could be an issue, like the items you mentioned, and paste them into a blank map. Take them out of your project and try again, if it works, add them back from the blank map until it doesn’t work to pinpoint the problem.
Could be a big slog, but if no one has a better suggestion or solution, it might help.