Hey! I know about this as well, but this is not a bug, it's just how the game handles you opening containers (chests & graves). That floating chest being there is intended and also not a problem either since it's only open when you have the inventory open.
Everything mentioned above has also been confirmed by one of the server's Quality Assurance members, so we know it is true. You can read the full response below.
This is intended
No need to make a bug report; the chest shouldn't be too bothersome as it appears behind you and disappears quickly after closing a chest
Hope this clears up things. Also, if you have any more questions, feel free to ask them!