Option exercise not possible. H.Rel. &1 in CoCd &2 already dedesignated

What causes this issue?

You are trying to exercise an option or to settle an exercise option.
The option is in a hedging relationship and the resulting forward
transaction should be added to the existing hedging relationship. The
dedesignation business transaction of this hedging relationship has
already been released with transaction <AB>TPM120.</>

System Response

The system doesn't allow you to exercise an option or to settle an
exercise option.

How to fix this error?

Use transaction <AB>TPM121</> first to reverse the release of the
corresponding dedesignation business transaction.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.