Bad_LocaleNotSupported should be reported by Write service
As indicated by Part 4 (v1.04) the result status BadLocaleNotSupported should be reported by Write service when a Client attempts to write a locale that is either syntactically invalid or not supported. The service was reporting another "generic" error code BadInvalidArgument. This was due to the fact that no value was defined for BadLocaleNotSupported result status which made impossible to return the proper value. The expected value is now defined as stated in the OPC UA foundation ticket 8933:
New Code: 0x80ED0000
It should then be used instead of BadInvalidArgument.