Shipment cost and invoice verification

Hi

I have two questions?

1. When the invoice process via transportation service agent is this only for service PO's item category D?

2. I have an issue. I created an inbound delivery, shipment and shipment cost.

when posting the GR updated the PO correctly and the invoice for the correct freight vendor

and value.

The second delivery/shipment had a different freight cost which updated the Po correctly

but when doing the invoice suggested the correct freight value posted in the PO but the difference between the first freight

value and second freight value posted half to the stock account.

Example first freight value was 10eur posted correctly in invoice,

second freight value was 11eur the posting in the invoice was debit 11eur from freight and credit 10.50 to vendor and .50 to stock

Can someone please help.

Thanks

Trevor