Im guessing that Redditor was me (Thahat)
also, i heared that templates dont currently store cuts in roofs propperly, so it might have to do with that.
The 3 high blocks inside what @Fornjotr said might be it too (though i havent looked at it, will do so when at home)
you could try that happens if you make the hallways have at least a 1x4 high air space from house to house and see it that helps. also, where do they stop building?