You are not able to move a client if the Active Directory structure contains accounts that do not have Symantec Endpoint Protection (SEP) installed.
"errorMessage": "Duplicate hardware keys found: [null]."
Hardware keys returning NULL as SEP is not installed.
This issue is resolved in Symantec Endpoint Protection (SEP) 14 MP2. For more information on upgrading, please see Upgrade or migrate to Endpoint Protection 14