Minecraft v1.12.2 Forge v184.108.40.20638 Effortless Building v2.13 Cray's Furniture v6.3.0
3D models tend to render weirdly. This includes both 3D resource packs and mods, such as with the furniture mod. It seems to affect all build modes. Generally, any block with a 3D model.
- Grab any piece of furniture.
- Switch to a build mode.
- Look at the preview.
In this case, I'm using the Jungle Desk Cabinet: