Upgrading for silver to diamond and gold to diamond are missing for the "Silver Silver Shulker Box". They exist in-game, but they're wrongly using the "Gray Silver Shulker Box".

So the recipes titled "shulker/gray/gold/silver_gold_shulker_box" and "shulker/silver/gold/silver_gold_shulker_box" are both using a gray box in the center. Same with respective silver to diamond recipes.