When the box is against a block it does not display the block when it is opened.
MC-122254 Shulker boxes placed against walls allow you to "see through" the wall when opened
MC-122267 Empty Void Behind Shulker Boxes When Opened
MC-122914 The texture of the lava and water is invisible when there is a block above
MC-123112 The top of walls are transparent when there is a skull above
MC-123598 Fence top missing texture when below fence gate