Changing, deleting, or adding an additional local currency in Other terms
a company code (OB22) may result in critical errors.
If additional local currencies are modified in a productive system, you may no longer be able to clear or pay already posted documents. Also, a system standstill may occur. In addition, postings of irreproducible exchange rate differences may occur. Data reconciliation can no longer be guaranteed.
Currently, the user is notified of this change only by a warning. Neither the warning nor the long text refer to possible consequences of the change.
These errors may occur even if you only change the valuation.
Such a change should only be performed if you also perform a currency changeover for all documents at the same time.
Transaction OB22, subsequent change, additional currency, document splitting, New G/L, currency changeover Solution
https://service.sap.com/sap/support/notes/1480453 (SAP Service marketplace login required)