Why EXPDP suddenly takes too long than usual? How to resolve this?

Oracle Database 11g
We have a expdp scheduled daily at 12am, the usual backup takes approximately 1 hour to complete. But suddenly it takes longer than usual approximately more than 10 hours. Below is the sample expdp line.

expdp system/********* directory=DATA_PUMP_DIR_BO dumpfile=FileName.'date +%Y%m%d'_%U.dmp schemas=SCHEMA1, SCHEMA2, SCHEMA3 logfile=$ORACLE.SID.FILENAME.'date +%Y%m%d'.expdp.log parallel=2;

Since it takes too long we decided to kill the job with below commands

1. attach to the job.
expdp system/********* attach=SYS_EXPORT_SCHEMA_40

2. Kill the job

kill_job

3. typed YES to confirm.

after confirmation, below error prompts