well it can post freight costs 

Yes freight is applied to correct GL account according to the special accounts. This has taking the Cost of Goods account from the sales department, which should only be used for sales, and applying it by some metric to a select few purchase orders. 

A regular purchase order GL transaction should be inventory, accounts payable, then any accrued amounts and taxes. But what I have here is a few PO's where the inventory got split up with the cost of goods account. 

have you looked at the actual journal entries to see which module the posts have come from 

Just getting back to this, but no I'm not missing anything. These are postings from the purchase order's typically from users with auto post turned on where seemingly at random from the items sales department setting instead of using the inventory account some small amount is being added from the cost account.

Redoing the PO, either copying it and re-issuing or even doing the original PO from a company backup, does not produce the same result but instead uses the inventory account as the system should.

Just getting back to this, but no I'm not missing anything. These are postings from the purchase order's typically from users with auto post turned on where seemingly at random from the items sales department setting instead of using the inventory account some small amount is being added from the cost account.

Redoing the PO, either copying it and re-issuing or even doing the original PO from a company backup, does not produce the same result but instead uses the inventory account as the system should.