Commitment item &3 in FM area &1 and Fyear &2 was already posted

What causes this issue?

Commitment item &V3& in FM area &V1& andd fiscal year &V2& was already
posted.

System Response

The chosen action is not executed.

How to fix this error?

IF &[SWITCH]PSM_FM_CI_CORE_REV_2& = 'X'.
For more detailed information, call transaction SLG1 and look at the
error log.
ENDIF.

Error message extract from SAP system. Copyright SAP SE.