The characteristic values of objects & and & do not match

What causes this issue?

The characteristic values of the source are not all defined in the
target.

System Response

The status for this object is set to "Checked with errors".
This object cannot be reclassified until the error has been
eliminated.

How to fix this error?

Check the characteristic values for the two objects and try to
maintain these so that they agree.

Error message extract from SAP system. Copyright SAP SE.