World flips between two versions

Could you add more information about the version - do you mean the point at which it's saved?

To make your bug report as effective as possible, please try and include the following steps to reproduce the problem:

Steps to Reproduce:
1.
2.
3.

Observed Results:
(Briefly describe what happens)

Expected Results:
(Briefly describe what should happen)

Quick Links:
📓 Issue Guidelines – 💬 Mojang Support – 📧 Suggestions – 📖 Minecraft Wiki

I have had this issue on two separate worlds several times.
Both are flat worlds, one is new and the other is a few years old. Both have filesizes of less than 1MB

Platform: Windows 10
MC Version: 1.19.51

Video taken from a recent Live stream highlighting the bug:
Video Link

What happens:
Opening the world the first time after loading Minecraft:
The world has reverted to an older state. Builds / chunks and items are missing. The player is in a different location from where they logged out.
Closing and opening the world for a second time:
The world is as expected. Blocks / chunks & items are back and the player is where they logged out.

To reproduce:
There is seemingly no consistent way to reproduce.

Steps taken in 1st scenario:
1. Open Minecraft (Windows 10 1.19.51)
2. Click play
3. Choose a world ( only had this issue with flat worlds so far)
4. Observe the world reverted to a previous state. (builds/chunks/items missing, player in wrong location)
5. Close the world
5. Open the same world
6. Observe the world back to its expected state

Steps taken in 2nd scenario (As per video link above)
1. Open Minecraft (Windows 10 1.19.51)
2. Click play
3. Play on a server
4. Exit the server
5. Choose a local world (only had this issue with flat worlds so far)
6. Observe the world reverted to a previous state. (builds/chunks/items missing, player in wrong location)
7. Close the world
8. Open the same world
9. Observe the world back to its expected state

I have had the issue from a world downloaded from a BDS server.

The server is running Ubuntu and my pc is running Windows 11.

For me, it was not a flat world. The file size of the world is just over 750MB.

EDIT: Since posting this comment it has also happened to a custom flat world, which as far as I remember has never been on a server/realm.

Thank you for your report!
We're tracking this issue in MCPE-164765, so this ticket is being resolved and linked as a duplicate.

If you would like to add a vote and any extra information to the main ticket it would be appreciated.

If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.

Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki
_{-- I am a bot. This action was performed automatically! The ticket was resolved by one of our moderators, and I left this message to give more information to you.}