Difference cannot now be posted (period & &)

What causes this issue?

For this <GL:physical_inventory_document>physical inventory document</>
the <GL:inventory_difference>differences</> had to be posted in period
&V1& (posting period in which the count results were entered). However,
this period is neither the current period nor the previous period. This
means that you cannot post any more documents in this period.

System Response

The posting of differences for this document is rejected by the system.
The physical inventory cannot be completed.

How to fix this error?

There are two possible ways of posting the differences:
Arrange a recount. Proceed as follows:
Arrange a recount for the physical inventory document. As a result, all
the items of this document will be deactivated and copied into a new
physical inventory document (recount document).
Enter the count results for the recount document.
Post the differences for the recount document.
Delete the items involved. Proceed as follows:
Choose the function "Physical inventory document -> Change", and
delete the items concerned.
Include the deleted items in a new physical inventory document.

Error message extract from SAP system. Copyright SAP SE.