EXPDP error ORA-39374 + ORA-13158 Oracle object does not exist
It is recommended to exclude statistics when doing an export. It is better to export the stats in a different way (DBMS_STATS) or re-gather once the data is imported. I know it does not solve the root cause, but Oracle actually recommends that you do not export the statistics. 

Try to do the export again with LOGTIME=ALL and METRICS=Y to get a better idea of what it is spending time on. Otherwise, you might have to turn on 10046 tracing to see what query it is stuck in. 

Do you have many objects (10.000+) to export or many partitions?