Based on the provided text, it appears that you are experiencing a bug where items purchased through an in-game item shop (likely Metin2) are not being saved correctly between server restarts or player logouts.

Here's a breakdown of key points:

1. Multiple game cores and channels running simultaneously

2. Each core has several active players at any given time

The main issue seems to be related to how the game generates unique IDs for items, particularly when multiple servers are involved in the same world (as indicated by references to 'server A' and 'server B').

When a player purchases an item on one server:

1. The game should assign a unique ID to that item.

2. However, due to some synchronization issue or perhaps a race condition during database updates between servers:

- The new item's details (including its assigned ID) are not immediately synchronized across all involved servers.

This leads to the following consequences:

3. When players log back in on another server within the same world:

- They find that their previously purchased items have vanished, as no record of those purchases exists yet on this second server.

4. The opposite also happens: when a player buys an item on one server but then logs into the game on another without proper synchronization between servers:

- That new item is not recognized or recorded correctly by other servers in the same world.

To address these issues, you may want to investigate further into your game's architecture and database management. Some possible solutions could include:

1. Implementing a more robust distributed ID generation mechanism across all involved servers.

2. Improving data synchronization between servers when players log on/off or perform certain actions (like buying/selling items).

3. Optimizing query performance for item-related operations in your MySQL database.

If you're still experiencing problems after implementing these changes, consider enabling detailed logging and monitoring tools to gather more specific information about the exact sequence of events leading up to this issue occurring. This will help identify any remaining bottlenecks or bugs that could be contributing factors.

Metin2 item shop forum