Degraded Resync???

I've been adding disks to the ReadyNAS RN628X to complete the array (goal is having 8 identical drives in RAID-6). I managed to get 2 drives ordered recently (I'll call them Disk 6 and Disk 7) and installed them to the respective slots (going in order here from top to bottom).

Disk 6 was installed, resynched, nothing strange found. It expanded the array to a 6-drive RAID-5 with no issue.

Disk 7 was installed after Disk 6 finished resynching. I get the usual "Reshaping Data" message... but when I check again, the box is saying "DATA DEGRADED" (I don't recall seeing that when I installed Disk 2 or Disk 3). Sure enough, I log into the box, and observe the following:

From Overview: Status reads "Degraded, volume resyncing" [sic]

From Volumes: The blue snapshot box has a notice over the "Resyncing in progress" line, saying "Volume is degraded".

From Performance: When looking at each disk for an overview, the indicators show green, no errors reported.

From Alarms: No warnings or errors at all. Info says the data resync is still in progress.

So to summarize, I have a ReadyNAS box that's emphatically telling me my array is degraded (while resync still goes on in the background... the usual "Data reshaping" readout is superseded... and the ReadyNAS OS is telling me "your data is degraded, but all your disks are perfectly fine. Oh, and resync is still going on, just that you'd only see that here and not in the box's readout."

Looking at the Logs, it looks like 3 minutes after I installed Disk 7... "Disk in channel 7 (Internal) changed state from RESYNC to ONLINE."

However, the resync seems to still be going on in the background (the progress percentage is slowly going up, and the "remaining time" is likewise slowly going down). So now I'm confused as to whether it's actually redoing the array while resynching the disk, or if the disk resync was somehow stopped when it wasn't supposed to be by the ReadyNAS system (but then why would the resync info refresh like that?)

Is this normal behavior for an array level change from RAID-5 (3 to 6 disks, I know) to RAID-6 (7 to 8 disks)? Should I just let it resync? Or is this a legitimate cause for concern? I wish I could remember whether I saw this when I added my third disk (thus making the array change from RAID 1 to RAID 5). I do remember seeing the "degraded" message temporarily while it synched the 2nd disk (changing it from JBOD to RAID 1), but only in the OS, not the box itself... but I digress.

Any help or input is appreciated.