We're playing minecraft again. Hosting our small world on the PC running Windows 10. ("Server" Player character conveniently stowed away)
Each Player connects using their own Android device, different devices running different versions.
When disconnecting & reconnecting every player spawns at his last postion, having their last inventory.

After the server Minecraft on the PC is closed, each player starts at the location of the host, with the same inventory as the host - the last inventory is lost.

Maybe related:

All Players are shown using as Names like [1],[2],[3] instead of the locally entered Name.

None of the players/devices are logged in to XBOX live.

The world has been begun on an Android device, the World files have been copied to the PC afterwards - this might be related.