Data model &1, entity type &2: Change of prefix

What causes this issue?

You have changed the prefix for a temporary key from &V3& to &V4&.
Either you changed the prefix explicitly, or you changed it implicitly
by deleting or adding a prefix while entity type &V2& is restricted to
internal key assignment (in this case, the default prefix is $).
This can lead to inconsistencies, if entities of type &V2& exist in the
system with temporary key values (which begin with the prefix &V3&).
This also affects all systems to which this Customizing is transported.

System Response

The change can be saved.

How to fix this error?

Check if the change is necessary, and undo the change if it is not
necessary.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.