Inventory linking producer

Hi all,

I have a client who is a primary producer. they grow the product and then have it packaged when ready for sale. 

In the inventory they linked a COS, Income and Asset account for the item to be sold. I have noticed when and invoice is raised it puts a cost against the COS account, income and reduces the stock. 

The problem is the item's packaging etc has already been paid to the supplier so there should not be an additional COS expense.

I have tried unticking the COS buy option but it makes no difference, every sale debits the COS line

It is affecting the Reporting as there is an expense line that did not occur. 

I am used to Inventory in MYOB with other clients but they are not producers.

Does anyone have any idea's for this issue?

Thanks for any help you can suggest