a client uses SAP 882 PL9.
stock item for which the last purchase price is not the actual last purchase price.
How does this happen and how can one fix it?

The last purchase price shows R32 / kg – which we bought in September 2013?

The note sap note 1358329 shows that it will not update if invoice backdated prior to the last date.
This is not the case here.
The note sap note 889702 wasn't much help either.
The only thing is that 2 transactions on the invoice, will this make a difference?