The problem is not in Cloning but Just in View of an already Created Item whose Code is Same as that of any GL Code.
To Reproduce the Error follow the steps below
Go to Iitems&Inventory>>Items
Create a New Item with Code 5800 and check the behavior.
There is already a GL Account with Code 5800 named Licenses.
Once you Create the Item and then Reopen it you will see this screen
While you see the above screen the Data in Database is absolutely correct. The problem is just in View of the related GL Codes for this Item.
Note: This installation is a Fresh installation with the Demo Data