Import Product with AIF

I’m trying to import some products via the AIF when using AX 2012. If I don’t set the default purchase/sales/invent site and location, it works fine, but when I try to set them I get the following exception thrown:

Cannot create a record in Item purchase order settings (OST). 
The record already exists.
Error found when validating record.
Cannot edit a record in Item purchase order settings (InventItemPurchSetup). Item number: 
1472, 00000002_078.
The record already exists.

The item I am trying to upload has an ItemId of 1472, hence why it is in the exception

Here is the code (I will just show the Purchase setup as the Sales and Invent are pretty much the same):

inventTable[0].InventItemPurchSetup = new[] { 
    new AxdEntity_InventItemPurchSetup {  
        ItemId = inventTable[0].ItemId,
        InventDimPurchSetup = new[] {
            new AxdEntity_InventDimPurchSetup
            {
                InventDimId = "AllBlank2"
            }
        },
        DefaultInventDimPurchSetup = new[] {
            new AxdEntity_DefaultInventDimPurchSetup
            {
                InventDimId = "AllBlank2",
                InventSiteId = "OST"
            }
        }
    },
    new AxdEntity_InventItemPurchSetup {  
        ItemId = inventTable[0].ItemId,
        InventDimPurchSetup = new[] {
            new AxdEntity_InventDimPurchSetup
            {
                InventSiteId = "OST"
            }
        },
        DefaultInventDimPurchSetup = new[] {
            new AxdEntity_DefaultInventDimPurchSetup
            {
                InventLocationId = "PER"
            }
        }
    }
};

Any ideas what I am doing wrong?