I have gotten that to work once, but it doesn’t work every time. I am still trying to figure out why it worked once and not since, maybe because everything was in one level the first time and sub levels after. Not sure. I do have a ton of materials in this scene as you do, but I have had this happen in a much less complex scene also.
It would be nice to know a real solution to this, or at least what could be causing it so it could be avoided. I am going to try migrating everything over from a single level and see if that works better. I wonder if I deleted the intermediate folder before I migrated the level over the one time too. There was something I did that made it work, just wish I remembered what it was. 