One of our clients had this issue when on version 2005 the system create foreign exchange for no reason...it was a known bug
They use to ammend it by reversing the additional journal entry.
Now the system reports an inconsistency on the debtor and the statement does not agree with the debtors balance.
And it gives an error reconciliation is unbalanced. Error 3821-8
They currently on 2007 patch 37, but will upgrading to patch 42 soon.