Thanks for the reply,

However, I have just been through the process of turning on chronology of stock, part of this process was to set my updating cost price at goods receipt radio button to weighted-average.
This was on the advice from Kaido, who said, everyone who is using weighted-average as their cost model should have the radio button set this way.
If you have your radio button set to last purchase cost, then the gross profit calculation on sales invoice will be different to the gross profit calculation done in the normal ledger!

There should really be an option on the maintenance routine, to be able to choose which cost is used when updating your purchase items.
Are there any other workarounds for this issue?