Anecdotal confirmation; I just experienced the same thing but on the Java edition, but can't find an equivalent bug report for it there, not sure what the routines are for issues that potentially affect both versions.
Placed two shulkerboxes inside the "captains cabin" area of a sunken ship while looting the chest in there and sorting items, and when I mined them again (with a fully enchanted diamond pickaxe), one was put into the inventory while the other was not. Tore the entire surrounding area apart trying to find it again in case it had glitched inside a block in the boat or something, but it had neither floated up nor sunk anywhere, and there were no dolphins in the area that could have joinked it. No invisible entities in my inventory, as it filled up completely with parts from the boat after.
This happened on a small multiplayer server, version 1.21.1
FrozenCorgi
Anecdotal confirmation; I just experienced the same thing but on the Java edition, but can't find an equivalent bug report for it there, not sure what the routines are for issues that potentially affect both versions.
Placed two shulkerboxes inside the "captains cabin" area of a sunken ship while looting the chest in there and sorting items, and when I mined them again (with a fully enchanted diamond pickaxe), one was put into the inventory while the other was not. Tore the entire surrounding area apart trying to find it again in case it had glitched inside a block in the boat or something, but it had neither floated up nor sunk anywhere, and there were no dolphins in the area that could have joinked it. No invisible entities in my inventory, as it filled up completely with parts from the boat after.
This happened on a small multiplayer server, version 1.21.1