On the inside of blocks with all inner faces (such as the spawner or vault) and only for certain sides, if I place a block touching the side, the opposite inner side gets culled while the inner of the one touching the block does not. I believe this is a bug as it is not the case for other sides of the block. I have attached an image to clear up any confusion in my description. See in the image how the inner face on the left side is culled while the inner face on the right (which is touching a block) is not culled.