Characteristic &1 is tied to characteristic &2

What causes this issue?

In the foreign key maintained in the customer enhancement, you
specified that characteristic &V1& is tied to characteristic &V2&.
This information was adopted by the characteristic catalog of the
drilldown.

System Response

If you choose characteristic &V1& for a drilldown report, then
characteristic &V2& also has to be used in the same report.
Selection using characteristic &V2& is prerequisite for selection using
characteristic &V1&.

Error message extract from SAP system. Copyright SAP SE.