Referencing or inheriting with specification type & is not permitted

What causes this issue?

Each <DS:GLOS.F87B3E882F18D4119B510060B0671ACC>specification</> is
assigned a <DS:GLOS.3526BF63AFAB52B9E10000009B38F974>specification type
</>. In Customizing, you specify for each specification type the types
of specification that can be used as sources in references and
inheritances. This means that only specifications of particular
specification types can be assigned to a specification in references and
inheritances.
The specification you assigned in a reference or inheritance belongs to
a specification type for which the required reference or inheritance
with the current specification is not possible for the following
reasons:
You entered a specification as a reference or source specification for
the current specification. In Customizing, the specification type of the
specified reference or source specification is not given as a permitted
source specification type for the specification type of the current
specification.
You entered a specification as a target specification for the current
specification. In Customizing, the specification type of the current
specification is not given as a permitted source specification type for
the specification type of the target specification specified.

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?

Enter a specification of a permitted specification type. If you want to
enter the specification that was originally assigned, contact your
system administrator.

Procedure for System Administrators

INCLUDE EHS_SAF_CHECK_CUSTOMIZING OBJECT DOKU ID TX

Error message extract from SAP system. Copyright SAP SE.