Platforms make rooms separate from house

@Elithian87 @FalconSims Hmmmm... the house I'm building has no need for platforms so I have only done experiments with them so far. When I read this post I tried what you mentioned and am not seeing the issue in my experiments to this point. This is what I've tried so far...

I used the home I've been doing platform, ladder and stair combo experiments in. In this 1st floor room there are three platforms of varied heights with stairs and ladders. One of the platforms is dragged downward for a sunken room effect, I think 2-3 steps downward. When I click the side of the large room that contains the platforms within it it highlights as one room, though all of the platforms look like separate areas. However...

When I choose to save this as a room... it does save the room with all three platform areas intact, though it does delete the ladder and stair parts in all of them...

Then I went to a different lot and placed the room on that lot. All of the platforms and room placed fine...

But I did find that above all of the platforms the ceiling was missing when placed.

I was able to plunk on a clunky huge roof... But even with the roof stuck on the holes remained.

So I did the trick I normally do to fill in a hole in the ceiling like this. Use the room or wall tool to make a room over the holes. This will create a floor that will become the ceiling for the hole area. Then just delete the walls on these new temp rooms. Also go up a level and delete the ceilings those rooms made or they'll be hanging around up there.

In your cases I'm assuming your rooms are different in some way(s). Can you provide screenshots of your lot and issue?