Expdp ORA-39126 KUPW$WORKER.FETCH_XML_OBJECTS ORA-01031

Hi, I am trying to export a database's metadata, but the export log shows...

Export: Release 11.2.0.4.0 - Production on Tue May 2 09:49:09 2017Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit ProductionWith the Partitioning, Oracle Label Security, OLAP and Oracle Database Vault optionsFLASHBACK automatically enabled to preserve database integrity.Starting "SYS"."SYS_EXPORT_FULL_02":  userid="/******** AS SYSDBA" full=y content=METADATA_ONLY directory=EXPORT_METADATA dumpfile=expdp_LNKQ11.20170502.094909.dmp logfile=expdp_LNKQ11.20170502.094909.logORA-39126: Worker unexpected fatal error in KUPW$WORKER.FETCH_XML_OBJECTS []ORA-01031: insufficient privilegesORA-06512: at "SYS.DBMS_SYS_ERROR", line 86ORA-06512: at "SYS.KUPW$WORKER", line 9710----- PL/SQL Call Stack -----  object      line  object  handle    number  name70001005be24c60     21979  package body SYS.KUPW$WORKER70001005be24c60      9742  package body SYS.KUPW$WORKER70001005be24c60     11838  package body SYS.KUPW$WORKER70001005be24c60      2808  package body