array:Unknown Md Area(Target) Raid Array cannot be mounted

[Rikart Garrigos]

Dear all, after a power issue I had two disks (HDD) damaged on my RAID 5. Fortunately the Hot spare has entered with success and the RAID is still kept alive. I have replaced the damaged HDDs by new units but the Raid 5 isn't able to rebuild with the second disk. I have the message below, when trying to add the second disk (I have changed the disk several times to discard issues). Any help would be appreciated.

RAID Error Notification

HDD error occurred
array:Unknown Md Area(Target)


RAID array can not be mounted.

[TeraStationInformation]
 TeraStationName: NAS003 (TS-2RZ)
 Time: 2015/09/03 10:28:32

[Rikart Garrigos]

I have changed disk 2 to another Bay and trying to rebuild the raid...But I cannot format the disk2 at all. Format error everytime...See below:

Because of an error, the following process did not complete.:Format Disk

So I'm not able to add disk2 to the RAID. This situation is killing me. A disk replacement is really complicated in the Terastation 7120r.

Please, any help on that would be appreciated.