This is resolved with the help of EMC support.
Resolution was to change the gateway priority of the multiple 1G network (subnet0) to 2 so that the backup traffic will go through the multiple 10G network.
So in ALL performance troubleshooting you have to look at ALL theorecticals.
Read Speed - Transfer Speed - Write Speed
If you feel that transfer network and storage speed is ok, I would focus on the read speed (As perhaps your NetApp is a better tiered device.)
From:
How to troubleshoot NDMP Backups failures when status code 99 (or other NDMP backup failure) is reported. Includes logging instructions.
Article: TECH56492
Updated: February 24, 2015
Article URL: http://www.symantec.com/docs/TECH56492
7. For performance issues, try backing up the path in the policy to a null device and note the timing:
NetApp: dump 0f null /vol/volname
EMC Celerra: server_archive <datamover name> -w -f /dev/null/ -J <file path>
If the Celerra command is not applicible for the Isilon, please see EMC for the correct command to attempt the dump to null to test local device speeds.
