Field & in table COKA cannot be changed

What causes this issue?

Via the planning data interface, you have tried to change field &v1& in
the table COKA from value &v2& to value &v3&. The planning data
interface does not allow changing the table COKA, that is you cannot
change the fields: Unit of measure (COKA-MEINH), Manage quantity
(COKA-MGEFL), and Cost element attribute via the interface.

System Response

The old values remain in the database.

How to fix this error?

If the field is to be changed nevertheless, use manual planning.

Error message extract from SAP system. Copyright SAP SE.