I have had this issue on a rare occasion for a good while now, but logging out and back in has always fixed it. Suddenly, it has gotten a lot worse. For a week or so now, I have been falling through teleporter tiles in my house. Stepping on a teleporter results in me visually falling through to the floor below - even though the teleporter should take me up to the next floor. Anyone else had this issue or know a work-around? I have areas of my house that are currently very difficult to access because of this.