When a Shulker Box with items is dropped onto lava, fire, cactus it will drop all items stored inside (This is likely to allow for some items like Netherite which may be immune to the offending damage to be salvaged).
When a Shulker Box is dropped into a Lava Cauldron it is directly destroyed and no items are dropped.
Process to Reproduce:
1) Create a Shulker Box with at least one Netherite item inside of it.
2) Break & pick it up with items inside.
3) Drop the Box into a Lava Cauldron
Expected Behavior:
Box drops the Netherite item which survives due to Lava damage immunity.
Actual Behavior:
Box is destroyed and the Netherite item is destroyed with it.
Cannot reproduce in Minecraft snapshot 25w04a