ERS and PO pricing

All,

Does anyone have any ideas on why ERS performs differently with POs than with SAs? In my testing ERS for POs - will use the price of the material at the time of settlement vs the time of the GR. Whereas for SAs it uses the price of the material at the time of the GR. Any idea why this is the case and if there is anyway we can influence which price it uses during settlement?

*Example for PO:*

price is 10.00/KG

GR is done

price changed to 20.00/KG

ERS settlement done and pricing is at 20.00/KG

Example for SA

price it 10.00/KG

GR is done

price changed to 20.00/KG

ERS settlement done and pricing is 10.00/KG

Regards,

Sandra