BDS 1.26.52.3 rewrites Block Entity data, causing rendering and input failure after restart

Summary

A long-running survival world becomes unusable in a specific large storage area after the area is loaded by a player, the player disconnects, BDS is stopped normally, and the world is loaded again.

The issue was reproduced using an unmodified Minecraft Bedrock v26.52 Windows client and an official clean installation of Bedrock Dedicated Server 1.26.52.3. No add-ons or behavior packs are involved.

Steps to Reproduce

1. Start BDS 1.26.52.3 with a known-good copy of the affected survival world.
2. Connect using the unmodified Minecraft Bedrock v26.52 Windows client.
3. Travel normally to the affected large storage area and load the chunks.
4. The area initially renders and operates normally.
5. Disconnect the player normally.
6. Stop BDS normally using the server console.
7. Restart BDS without making any changes to the world.
8. Reconnect at the affected location.

Expected Result

The world should load normally and remain playable after restarting the server.

Actual Result

After reconnecting, severe rendering corruption occurs. Large parts of the world fail to render. Player movement may work for a few blocks immediately after joining, but shortly afterward normal player input stops responding.

Restoring the known-good copy restores normal operation. Repeating the same procedure causes the problem again.

The same behavior was previously observed with BDS 1.26.51.1. It was independently reproduced again from a known-good copy using a clean BDS 1.26.52.3 installation.

Additional Diagnostic Information

Starting and stopping BDS 1.26.52.3 without any player connecting does not trigger the problem.

After reproducing the issue using only the unmodified client and official BDS, I performed a read-only comparison of copies of the world data. This analysis was performed only after the issue had already been reproduced and was not required to trigger the bug.

The comparison showed large changes to existing Chest, Barrel, and Shulker Box Block Entity data after the affected chunks had been loaded. The changes particularly involved the pairlead and forceunpair fields.

Detailed comparison results can be provided if useful for investigation.