Fill the double chest with lots of items
Break one of them
And the other one will look like you see in screenshots
When you do this one of the chests will be open as you see in the screenshots. Just get back to normal when interacting with him again.
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I discovered this visual bug after breaking one of my chests full of items

Thank you for your report!
We're going to track this issue at MCPE-96089, so I will resolve and link this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
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