Datapump export from remote database fail when parallel degree > 1

Oracle DB = 11.2.0.3 (both - source and target)RAC = 3 nodes(target)
RAC = 2 nodes(source)
OS= RH LINUX 6
ISSUE: the datapump export fails when I run in parallel. it complte without any issue when parallel=1

I need to export many schemas from the source DB into target DB. the size of total export is around 3 TB with 20 different schemas.

EXPDP parfile:

userid=testdatapump/password
DUMPFILE=exp_hospitals_from_qadb_%U.dmp
DIRECTORY=remote_datapump_dir
LOGFILE=exp_hospitals_from_qadb.log
FILESIZE=20g
SCHEMAS=hospitals
PARALLEL=4
NETWORK_LINK=dsdb_remote

ERRORS:
Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA
ORA-39126: Worker unexpected fatal error in KUPW$WORKER.MAIN []