When opening any container (including inventory), or any menu, there is a certain chance (depending on how long the world/realm has been open) that instead of the menu or container UI you wanted to see, you will be met with a loading icon, while in this state all player functions including: toolbar, both interact buttons, and the ability to open any other container/menu will persist. This icon will not go away unless the player exits the game via the Home Screen. (Sometimes you can escape this loading error with time but when you try to open anything afterwards it will return). Entering the nether while in this state will only further limit what the player can do (movement becomes impossible and trying to view different perspectives is met with a red screen plus previously mentioned issues). I have no record of when this bug started occurring but I cannot find any other indication of its existence aside from people I'm playing with which might mean this only happens to players in a realm who do not own said realm.

Due to the randomness of this bug I cannot provide a direct picture at the time of submitting this bug however, I can and will update this report with picture when I can.
I am including a picture of a similar loading icon that can persist outside of the game when attempting to join a realm

Edit: after playing all day on my realm I have gotten the bug to appear I will include pictures below: