seagate blackarmor nas 440/420 series 8 TB

Disc 3 sometimes gives error

The Seagate® BlackArmor® NAS 440/420 storage server is a complete, small-business-specific network storage solution designed to provide optimum uptime and data integrity to ensure business continuity for up to 50 workstations. Continuously and automatically protect business-critical data with incremental and full-system backup, bare metal restore (full-system restore) and individual file to entire volume encryption. Enhance data integrity and/or performance with RAID 0/1/5/10 & JBOD configuration options. Access files securely over the internet from any popular web browser — no special software required. Includes four energy efficient, reliable Seagate® hard drives. All four drives are easily removable without tools and hot-swappable to optimize uptime and data availability. Backed by a 3-year limited warranty from Seagate, the world leader in storage technology.