When joining a realm, there is a period of time in which the user can click the "cancel" button to stop the joining process, but as I have observed (with 1.16.1), this does not stop the client's attempt to join. Often, I will be on the title screen and the game will suddenly put me into the realm that I attempted to stop joining moments ago.

   This bug can become even stranger if the user is to join or load one of their own personal worlds. The player will be logged into the local save, but moments later (after the realm login request completes), the player will also be logged into the realm. This creates a strange state where the player is in a limbo between the two worlds, with visuals and inventory matching that of the realm, but block solidity and privileges of the local world. The big issue here is that while in the realm, the player will match the same relative location as in the local save world. This means that they will clip through blocks and run into invisible obstacles not seen. Along with collision, the bounding box also highlights blocks in the local world.

The sun will flash between the two world's game times roughly 3 times each second. As far as I can tell, chat is only in the local saved world. The affected player can run administrator commands despite not having those privileges in the realm.

While in this limbo state, I was able to open my world to LAN and log in with another account. The other account was able to see the Limbo'ed player and interact with him in the local world. Particle effects made from the alt jumping or placing blocks could be seen suspended in mid-air with the affected player.

In the attachments, you can see that I set up a dropper dropping arrows to the player in limbo. This demonstrates the shared particle and item effects mentioned above.

How to set up this bug for yourself:

1. Join a realm, but cancel it before you are joined.
2. Sit on the menu or title screen and wait. The player will be put into the realm after a few moments.
3. OR load a local saved world. Stand in the world a bit and wait. You should also join the reams world after awhile, being put into a limbo state.

Several other notes:

Attempting to leave while in this state locks the client on the "saving world" screen, and it must be ended with a process killer. The same thing happens if the internet connection is lost, but instead, the screen will be dark grey.

One time, I was able to interact with chests in the realms server, and the changes carried through when I got back on legitimately, but as I troubleshoot now, I cannot.

When re-joining, my player's position was the same as before the Limbo session.

I cannot access the "tab" menu while in limbo.

When joining the realm, the player in the local world is teleported to the coordinates of where the player is in the realm.

Along the top of the screen in the window bar, it will display the following text:

• Singleplayer if a local world was joined first
• Multiplayer (LAN) if opened to LAN
• Multiplayer (3rd party server) if internet connection is lost