3618304 - "Invalid mapping error" when viewing or saving the transformation of Market Communication for Utilities target system in IPS.

When viewing or saving the transformation of Market Communication for Utilities target system, error "Invalid mapping error" occurred.

The involved transformation entry between the mentioned lines contains "valueMappings".
For example: 

{

                "targetPath": "$.ROLE_NAME",

                "targetVariable": "entityIdTargetSystem",

                "type": "valueMapping",

                "sourcePaths": [

                                "$.displayName"

                ],

                "valueMappings": [

                                {

                                                "key": [

                                                                "<key>"

                                                ],

                                                "mappedValue": "<mapped value>"

                                }
......

                ]

}

Identity Provisioning

defaultValue, valuemapping, IAS, IPS, Invalid mapping error, Market Communication for Utilities , KBA , BC-IAM-IPS , Identity Provisioning Service (IPS) , Problem