I'd like you to do a few things so we can help debug the problem:
1. Start a server with no addons whatsoever, type trace(1); into the console. After that, play normally for a bit. Save the console log into another folder.
2. Start up the game with just the item storage mod, type trace(1); into the console. After that, play normally for a bit. Save the console log into the same folder as the other one.
3. Name them appropriately, like "without itemstorage" and "with itemstorage"
4. Upload them both.