The full error (according to the doc) reads:
ORA-31672: Worker process string died unexpectedly.
Cause: A Data Pump process model worker process died unexpectedly, so PMON
is cleaning up the process.
Action: Check your system for problems. Check the trace file for the process, if
one was created, for any additional information. Correct the error, if possible, and
try the operation again. If the error occurs again, contact Oracle Customer Support
and report the error.
The way this reads, there is no quick fix. Follow the suggestions above and then open a TAR with Oracle non-support.
note – “string” should be the name of the process in the full message that Oracle gave you, so use that name when searching the trace files.
Please provide as much information as possible when asking for help.
If you were performing an import with Data Pump which involved materialized views, then, according to Metalink doc 750702.1, the problem could be due to bug 5881123.
If that’s the case, you need to check for the availability of Patch 5881123 for your platform and version, or contact Oracle support.