A SATA reset has been performed on one or more of your disks

A disk (or maybe more than one) probably is failing. What is the SMART+ status for each of your disks under Status > Health in Frontview?

Each Smart+ status has a number of fields, some which have numbers. What should I relate? One disk has a count of 26 for something labeled "UDMA CRC Error Count" One has a number 2 next to "Retries" -

Is there a way to upload image files to this forum?

You can link in images that are stored on another web site, but you can't upload the images directly to here.

"CRC" is a "cyclical redundancy check". The stat suggests that there were 26 times when the data was garbled as it was transferred to/from the disk to the NAS. The issue was in the SATA interface, not reading/writing the disk media itself - so this is might not be the drive, it could be the NAS hardware. None of my disks report UDMA CRC errors.

Do you also see 2 hard disk resets on the drive that has 2 retries? One of my drives has 1 retry, and also 1 hard disk reset. I am thinking that this is actually what was reported by Frontview (count=2, two messages...)

My advice is to make or update your backup, and keep it current. If the error continues (particularly if it starts happening more often), I'd replace the disk. You could of course replace it now (but don't neglect the backup).