HS-DHTGL/R5 - backup ran all week, but only 1/3 complete and red light on drive

[csdjw]

Terastation HS-DHTGL/R5, firmware 2.14

I created a backup job to an external USB drive last week, and ran it "immediately". Today I unplugged the usb drive, never imagining that it would not be done, and checked the backup to find that only 1/3 of it was completed.

The web interface still says "Currently a backup is being carried out." and "Running Backup Job". The little yellow tools icon does not appear so I canot pause or delete the job.

Also, there is a red light next to drive one on the front of the server. There is also a RAID error reported: "Error has occurred in RAID Array1", and when I click on that it says, "An error in a RAID Array has been detected.
Select restructuring disk and click `Restructuring RAID Array`."

There is an unchecked box next to disk 1. Upon checking, the option to restructure is active. But I do not want to try and troubleshoot our server before an external backup is complete.

So my questions are, do backups normally take so long? Is there a faster way to backup? How can I complete the backup?

And then, will "restructuring" fix the RAID problem?

Thanks in advance for any suggestions!