Does it seem to happen after you update? If you launch a mod, people download it and use it, then you change something in the engrams/folder structure etc and some people can use it while other cannot it seems like a bug that I have seen. After spending hours trying to figure out why it happened to my mod, I changed the description and reuploaded and that fixed the problem. Its like the game is randomly choosing to not update properly at times when downloading mod updates. I’ve not seen it happen with one mod or solo so it might be a mod load order issue.