world completely breaks when using 2 accounts

When i was experimenting with multiple accounts, i logged onto the same world with 2 accounts, then moved one a bit, logged off of that one, and started a lan world on the other one. Joined with the second account again (on lan) and logged off. Now my world completely broke: buildings are cut in half, some things have "duplicated" on the map, etc. Now the whole world is corrupted.

 

video link: https://youtu.be/IEOZf5hIuZo (file is over 10 mb) of the corrupted world