Can't place itemframe on furniture

It's a Minecraft behaviour, the game is forcefully making itemframe removed because it is inside another entity, in this case the furniture itemframe.

Solution#

Reduce the furniture itemframe height of 0.1.
For example 1 -> 0.9, 2 -> 1.9 etc.

        hitbox:
          length: 1
          width: 1
          height: 1.9