RN214 Disk Failure Message but Healthy SMART Data

Hello,

After an unrelated power incident yesterday, my RN214 was shut down ungracefully. After the outage, it resynced the array and functioned normally for a few hours. Early this morning, it was stuck showing "Recover data 0.00%" on the LCD front panel. At this time it wasn't responsive over the network (could not ping it) nor could I interact with it through the power button. There was no disk activity. I cycled the power and was able to get into the web interface, but it started the recovery process again and began to report that one of the three installed disks was failing. However, the SMART data from the indicated disk shows that it is healthy.

It is making progress on the recovery and should finish in about 30 hours. I'm looking for help on the following: is the disk really failing if the SMART data is reading healthy? How do I prevent this from happening again? It doesn't seem healthy for the array to have to rebuild itself over and over, and I wouldn't want it to lock up again during a rebuild. I run monthly disk tests, defrags, volume scrubs, and balances, and did not have any performance issues or error messages preceeding the event. I'd appreciate any help or insight into this!

Here is some more information about my configuration:

ReadyNAS 214 with 3x 4TB WD Red Pro HDDs

with 5,000-6,000 power-on hours each

in RAID 5 under X-RAID

with 1 traditional volume (no iSCSI LUNS)

of 7.25 TB capacity with 2.3 TB free space

Thanks!