A vertical part of the map seems to be undiscoverable anymore. Even if I re-explore it (and it does get properly explored), reloading the world breaks it again.
I will attach the save file for this world. Please fix this, this is the second time this happens on a late-game world and I really, really don't want to lose all of this progress again. I do play with mods enabled but I'm positive it wasn't caused by mods.