It's usually caused by a mod conflict. Too many ENEX markers will cause spawning in other weird places because there is a game limit to the number of ENEX markers that can be used at one time. The "Enterable Buildings Mod" adds many ENEX markers and some other mods do this as well. If you already have something like these installed, then adding my ENEX markers will break that limit. Disable or remove other mods that edit or add ENEX markers, then try again.