When building with version 2018.1.0b13 of unity, trying a build after opening the aiutility editor, build will attempt to build into scene a hideflags.dontsave object, causing an error. Have to close Ai editor window, restart unity, then build. Took me a while to figure that one out. Using windows 10 .net framework 4.*
Not a big deal, but i hit my head against a wall for an hour or two trying to find the problem.