[Trexmaster]

If you open up a Portable Science Kit, or any other tools that bring up the talk menu with Build Mode's tab open, and you close Build Mode while still having said talk menu open, you won't be able to bring Build Mode back up until you leave the house.

You'll still be able to place the last tile you had selected, and move furniture (probably), despite the Build Mode tab being closed.

[Neus]

This has been corrected.