Compatibility Issue: Traveler's Backpack item disappears when re-entering world with Very Many Players mod

[Chopits-Kinako]

Describe the bug
When using Very Many Players (v mc1.21.8-0.2.0+beta.7.207) alongside Traveler's Backpack, the equipped Traveler's Backpack item disappears from the player after leaving and then re-joining a world/server.

To Reproduce
Steps to reproduce the behavior:

1. Start a world with both Very Many Players and Traveler's Backpack mods installed.
2. Obtain a Traveler's Backpack item and equip it.
3. Exit the world/server completely.
4. Re-enter the same world/server.
5. Observe that the previously equipped Traveler's Backpack is now missing from the player.

Expected behavior
The equipped Traveler's Backpack should remain on the player and persist its inventory and state after leaving and re-entering the world/server.

Runtime info (please complete the following information):

• OS: Windows 11
• Minecraft version: 1.21.8
• Mod version: mc1.21.8-0.2.0+beta.7.207
• Mod branch: beta

Crash reports / logs
minecraft-exported-logs-2025-10-24T22-32-31.log

Other mods
mod lists.txt

Checklist

• I am using the official version of the mod.
• I tried the latest development version but the issue persists.
• I searched for similar open issues and could not find an existing bug report on this.

Additional context
This issue occurs specifically with the interaction between these two mods. The game does not crash, but the backpack item is lost.