When i was building my house I noticed that the floors did not sound like floors nor did they give me the movement bonus I would expect from floors, they also made my friends sink down to their ankles in it as well. The floors also gave the characteristics of the terrain below the floor and not the floor itself. I thought the floors would act like floor boards and give a woody sound and give me a movement speed bonus aswell as make my friends stay ontop of them. To reproduce the bug build a house, the walls and the wooden floors ontop of any terrain and walk on them and see how they give you the sound and movement speed of the terrain you put them ontop of, in my case it was grass.