Reply to Kumasasa's comment: I did not change any of this and it worked, and it is a half-slab over the bed and not a stair. (I have not made any searching/testing so I can't really confirm to much about if you need 2 blocks of air above)
Reply to Michael Smith's comment: I moved the bookcase and it worked, thank you so much.
Yes, it has happened when I placed it aside another half-slab that was placed correctly.
It happened to myself and it keep happening to pretty much every youtuber I'm watching.