What causes this issue?

The system tries to save the object although no explicit changes have
been made to the object.
The reasons for this can be as follows:
The BRF knows dependent tables (such as TBRF200) that the system fills
based on the data of the current object.
It is possible that the actual object definition is correct but that the
dependent tables have not been filled correctly. If you perform a
where-used search, for example, this can lead to errors.
Many BRF object types can fill some data of the object-specific tables
independently. For example, result typing in the expression type
<ZK>Simple Value Request</> (implementing class 0SM001) is already
defined by the specification of a field of a DDIC structure. In the
scope of corrections, such automated steps can be made more precise as
required.

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?

The procedure depends on the namespace in which you are working:
If the object belongs to the customer namespace, take the following
steps:
Call the object in change mode.
Save the object directly.
If the object belongs to the SAP customer namespace, the object is
updated automatically by the support packages that are imported.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.