Don't know if this is a bug or not but when building my first base I first installed a corner then a wall next to it and put a ceiling tile aligned to the wall. When I put up the next ceiling tile over the corner it hangs over the edge of the corner. I can post pictures if somebody can tell me where they are saved to. BTW I am using the GOG version of 0.8.
Never mind, I found the screenshots I took but still don't know how to post them.