Foreign CPA and PR's calculating to many decimal places - causing PO change and approval issues

Oracle R12.2.3 (primary book GBP)

Apologies if this is the incorrect MOSC group (couldn't find a dedicated Purchasing Group).

We are experiencing issues when we update the requestor on a PO whereby the CPA has expired and we need to extend the end date to change the PO requestor (appreciate this may be a process issue in that a CPA should be valid if PO's are still active but that's for another day!).  When we try and approve the CPA we receive the above error and the only way round this is to increase the CPA by a nominal amount to allow approval.  As a result we are having CPA values that do not match our contract values (albeit