All Hard drive LED Flashing green synchronously - Raid rebuilding?

[metaverse]

Hello there,
I have following query:
I have 6604T NAS with 4 x 4TB HDD. One of HDD had bad sector which caused Raid to failed and started showing: System Error in ADM panel under RAID configuration section.
So I replaced faulty HDD. New HDD started flashing greee after every few seconds. After 15 minutes or so, all 4 HDD starting blinking green every 10 seconds. Does this mean , NAS rebuilding its RAID? and faulty HDD is getting synconised.
When I connect to NAS over web or do any action on NAS. It intrurpts this all 4 HDD flashing.
I have checked this issue/query over then internet as well as on forum but couldnt find any the solution.
Can any one please let me know what does the all 4 hard disk blinking in synchronised way means?

Also, how can I rebuild the RAID?

Thanks

[Nazar78]

Yes it's rebuilding for the next few hours, you can check its status in the Storage Manager. I guess your RAID is probably RAID 5 (striping + parity) which requires all disks to be accessed when rebuilding/synchronizing.

[metaverse]

Thank you for repluy @nazar.
Issue has been solved by Asustor team over remote access