missing items from inventory / missing items from items.txt

[xSL0W]

Describe the bug
Im using shopcore for a big module that creates 1000 items, a WS made for shopcore. Basically you buy skins from !shop.
The plugin starts registering items into shop OnPluginStart, only 1 time per server restart.
Some time ago a few players reported that their items are missing from their inventories. Some of the items dissapear immediately after buying. It happened to me too, a while ago. I've dig into the source code and found a file, called items.txt
I dont understand its purpose 100% but it looks like a disk-stored local db for the registered items, here is my file ( https://hatebin.com/aoyviwlnrv )
There are many items missing, many skins and stuff from this file.
I've looked into my mysql database and there are 1628 items registered here, I think its fine here.

To Reproduce
Steps to reproduce the behavior:

• Not sure how the items dissapear, its happens rarely and i couldn't find a pattern.

Expected behavior

• Skins to be saved into the inventory & items to appear in items.txt

Screenshots

• No screenshots

Server (please complete the following information):

• OS: debian10
• Sourcemod version 1.10.0.6501
• Version : plugin: 3.0E2

Additional context
Here is how i register items into shop. https://drive.google.com/file/d/1C760Rz28Zi_PklSqT5NTIgIADIuDfaTV/view?usp=sharing
Am I doing anything wrong?
Do I need to use forward public void Shop_Started() ? I can get rid of the timers, since that code is bad.