everything.
but more seriously, I believe this is because of the building you designed. unless something was changed with the build tools, you can’t make rooms or interior exteriors (lol) right now. the roofing gets really confused when you try to do that. I don’t know what the safety flag is, but I think that just confused the system even more by putting it “inside” the building in an area that is technically “outside” of it.
my suggestion is… don’t do that. the build tool is fragile right now. try not to make anything too fancy unless you wanna do it out of almost entirely through the slab tool.
that said, I have not played A14 yet (I’ve got too much stuff to do, like reading Mushoku Tensei and playing Tales of Xillia/Xillia 2/Zestiria… I mean uh, college. yea. college.), and I’m not an expert on building-related bugs (I love making creative buildings and it hurts to look at the bugs stopping me from making creative buildings lol). one of the mods could probably give a better answer.