Update!!
I was able to resore a backup and on the Xbox One. I got back my inventory, my location and my Ender Chest inventory.
I still won't use a different device to play unil I know that this issue is resolved.
After my problems listed yesterday. It is determined that replacing the realm with a backup results in error message. This needs to get fixed or I will be cancelling my realm here shortly.
I logged in on Switch into my realm. Inventory and levels were erased. When I relogged into my Xbox, inventory and Ender chest contents were gone. When I logged into the Windows 10 edition levels, location, inventory and Ender chest inventory was all reset - as if I was a brand new player to the Realm. I am attempting to replace realm with a backup. But I am getting a ridiculously long loading screen.
This is really BAD.
Same thing happened to me. I had the totem of undying in my off hand while fighting the Ender Dragon. I was under the Dragon's Breath effect. I died. The totem had its animation on my screen. All my items fell down. I then respawned in the overworld with none of my stuff. Is this supposed to happen?