Cost distribution f. grouping WBS & already executed in periods &2 &3

What causes this issue?

Cost distribution for grouping WBS element &V1& has already taken place
for period &V2&, year &V3&. You cannot perform cost distribution for an
earlier period.

System Response

Grouping WBS element &V1& is excluded from processing, as are all
production orders and purchase orders belonging to that element.

How to fix this error?

Reperform cost distribution for period &V2&. All costs incurred in the
meantime will be posted to this period.

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.