Since I likely wont since as far as I can tell it's not effecting anything else in-game and I don't feel like doing that method 1 by 1 to simply replace the stairs to a place I'll rarely go when I can just Tcl. Before that I installed plenty of mods (btw, including proto vault suit and badass vault-suits & coats, though I never used the latter ones in the end) but was upset and kinda surprised I couldnt find any mods that allowed for good customization of vault suits. Yeah, I knew all this, I was just trying to beat around having to actually do that. About 10 months ago I started my still ongoing FO4 playthrough. The only way to find it is to uninstall (NOT disable) your mods a few at a time until you find the culprit. I hope I'm making myself clear but the TL DR version is 'ANY mod can cause this'.
If the author didn't bother to clean them before release, then any garbage that was in the old mod would get carried over to the new. These plugins were then edited to work with the new mod. A lot of mods were created with FO4Edit and some used plugin files that were actually from another mod. ANY mod can cause issues if there are 'dirty edits' present in the plugin. Originally posted by SuperSledgeNY:Kray, it's definitely a mod and it doesn't have to be a mod that directly affects Vault 81.