Supplier Balance Not matching -Due to Foreign currency exchange rate difference -R12.1.3

Our application version is R12.1.3

We have supplier invoice in foreign currency.

Say example  -  our supplier provided invoice in USD.. Our  functional currency is KWD.

If the original invoice is in foreign paid/received in full and applied, system has to transfer the exchange variance automatically to Difference in exchange account and make vendor/Customer balance payable as Zero for that particular invoice.

But as of now in our system vendor account is showing exchange difference as due on supplier account.

Any solution is already identified for this issue

Thanks