Sum Not Working Correctly

Hi,
I have the following simple SP..

There is a field which I'm doing a sUM() on to get a total for a QtyRecieved from one of the tbls in the SP..
However, the QtyRecieved field is set to be a two decimal place numeric field.


The sp works fine without issues until on the of the qty received is not a round number.

If it's a number with a decimal in it (i.e 5.5) then this is show as a seperate result and not SUM'd with the others.

Any ideas why?

SELECT PDS_Login.Supplier_Products.ProductName, PDS_Login.Supplier_Products.ProductCode, dbo.Suppliers_POs_Details.POID,
dbo.Suppliers_POs_Details.PODetailsID, dbo.Suppliers_POs_Details.Qty, dbo.Suppliers_POs_Details.PricePerItem,
dbo.Suppliers_POs_Details.PoDetailsStatus, dbo.Suppliers_POs_Details.PoDateExpected, dbo.Suppliers_POs_Details.PODateReceived,
PDS_Login.Supplier_Products.UOM, PDS_Login.Supplier_Products.Vatable, dbo.Suppliers_POs_Details.ProductID,
dbo.Suppliers_POs_Details.PODetailsStatusReason, SUM(dbo.Suppliers_POs_Details_Received.Qty) AS QtyReceived
FROM PDS_Login.Supplier_Products INNER JOIN
dbo.Suppliers_POs_Details ON PDS_Login.Supplier_Products.ProductID = dbo.Suppliers_POs_Details.ProductID RIGHT OUTER JOIN
dbo.Suppliers_POs_Details_Received ON dbo.Suppliers_POs_Details.PODetailsID = dbo.Suppliers_POs_Details_Received.PODetailsID
GROUP BY dbo.Suppliers_POs_Details.PODetailsID, dbo.Suppliers_POs_Details.Qty, PDS_Login.Supplier_Products.ProductName,
PDS_Login.Supplier_Products.ProductCode, dbo.Suppliers_POs_Details.POID, dbo.Suppliers_POs_Details.PricePerItem,
dbo.Suppliers_POs_Details.PoDetailsStatus, dbo.Suppliers_POs_Details.PoDateExpected, dbo.Suppliers_POs_Details.PODateReceived,
PDS_Login.Supplier_Products.UOM, PDS_Login.Supplier_Products.Vatable, dbo.Suppliers_POs_Details.ProductID,
dbo.Suppliers_POs_Details.PODetailsStatusReason, dbo.Suppliers_POs_Details_Received.Qty
HAVING (dbo.Suppliers_POs_Details.POID = @POID)