This only happens on 1.16.100. Randomly when traveling in and out of the nether one of my double chests will appear as a singular chest. There will be an outline of the full chest but when you try to open the chest it usually crashes the game. Also when you click on the singular part of the chest it only shows the top slots of the double chest but when you click on the unrendered part it shows all the slots. The only solution I have found is to destroy and replace the chest. The world was created in the previous version.
World download linkprovided in this comment.