When I place roof's on my houses (not using the auto-roof) often the edges of the roof will poke through adjacent walls. In the past the game has known to cut off the roof at the wall but lately it hasn't been doing so and I can't for the life of me figure out why.

I only have the base game, and am playing on a macbook pro.

I do have downloaded objects, but I haven't added anything new in a while and as far as I know the misbehaving roof's does not coincide with adding any downloads.

I thought maybe it was because i'd used the moveObjects on cheat, but even after turning that off the roofs are still misbehaving.

The edges do usually go through the walls, they shouldn't impede the sims, and you should only see it if you have the walls up. I've found the roof will cut off if your building something like your own dormers, put the walls up first then run the roof tool over the whole thing and it cuts out the roof for the room areas.

That's the thing, though, it's not cutting off when it should. Ever. If I do that -- make my own dormers then run the roof tool over it -- the roof isn't cut off in the rooms. It's still there.