Video reproduction:
So a summary of the bug is: When you try to place furniture inside of a house that you’re still building, it gives you an X meaning you can place it. I’ve noticed however, after the floor of the building is made, you can then place furniture inside the building, but depending on the size, it may be impossible to save it before they finish building, my building however will have plenty of time to do so. I just find it much of a hassle to not be able to put chairs, tables, and beds in before the building is even being constructed.