When placing a block next to a spawner/trail spawner (use a translucent block to avoid MC-266463) the opposite face will become shaded as if the block was placed on the other side. This occurs in all directions (X/Y/Z) unlike the culling bug I mentioned earlier.

This issue doesn't affect vault blocks (mentioning this because they have a similar model so maybe this can be fixed by copying their behavior)

Check attached files for a showcase