I had the same issue with a DS-2CD2346G2-IU running V5.5.134 build 200430 (the latest release for that camera ... no V5.6.x available yet) with my NAS server (an HPE ProLiant Microserver running SmartOS from Joyent) serving a ZFS filesystem via NFSv3
My NFS "Net HDD" was showing "Normal" after...