Partial foreign key selected (select only one alternative)

What causes this issue?

You created a foreign key field and also marked the foreign key as a
partial foreign key by setting the <LS>Generic</> flag.
For partial foreign keys, the fields marked as generic are removed from
the allocation to the key fields of the check table. The check is then
only for the remaining fields.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Remove the entries for the foreign key field in the <LS>For.key table
</> or <LS>Foreign key field</> column or reset the <LS>Generic</>
flag.

Error message extract from SAP system. Copyright SAP SE.