I don't know what happened... maybe the new patch? This is going to take some explaining.
First, I noticed that all houses around the house I was customizing disappeared when I entered customization mode. This has never happened before. Also, my client has crashed twice in customization mode today, and the system seems to be super messed up now. The main issue I noticed was staircase placement inside a house. See the screenshots below.

The screenshot above is perfectly normal. All is well. But then...

After you place the staircase, the top half disappears. Since deleting the stairs goes unit by unit, you have no way of deleting the top half of the staircase.
The next two screenshots illustrate the issue...

Here I am on the 2nd floor of the house. Look closely, and you'll see the tops of the staircases just hovering there, unsupported. There's no way to delete them because they are not visible on the 1st floor.

Ummmmmm........ !?!?
First, I noticed that all houses around the house I was customizing disappeared when I entered customization mode. This has never happened before. Also, my client has crashed twice in customization mode today, and the system seems to be super messed up now. The main issue I noticed was staircase placement inside a house. See the screenshots below.

The screenshot above is perfectly normal. All is well. But then...

After you place the staircase, the top half disappears. Since deleting the stairs goes unit by unit, you have no way of deleting the top half of the staircase.
The next two screenshots illustrate the issue...

Here I am on the 2nd floor of the house. Look closely, and you'll see the tops of the staircases just hovering there, unsupported. There's no way to delete them because they are not visible on the 1st floor.

Ummmmmm........ !?!?