"Storage system verify or repair failed. : (-69716)"

I don't think "bad code on the update" is a likely cause. The user files on the data portion of the drive are in a separate volume from the sealed (read-only) MacOS itself. So bad code on the update would result in a poorly running OS, if it would run at all.

Disk First Aid checks the integrity of the file system (file catalog). A corrupted or damaged file somewhere in the data portion could cause this, or damage to the file system -- or physical damage to the drive.

Was your clean install a complete reformat/erase? Because if it was, this error returning seems most likely due to physical damage to the drive. But you can learn more about this by running DriveDX, which checks the hardware integrity of the drive. It can check fusion drives. Fusion drives have reportedly had a higher failure rate than SSDs or HDDs. Run the long test offered by DriveDX, I have seen drives that pass the short test but failed the long test.

Is this a Fusion Drive ?

Has the Fusion in the Fusion Drive been properly joined ?

How to fix a split Fusion Drive - Apple Support (CA)

CharlieBrad wrote:

I did complete the split drive routine at the time. DriveDX is a utility app to inspect the health of your drives and determine if you have a physical problem with your drive or a software issue. After receiving the rather spurious test info from DriveDX last night, I did a simple restart and repeated the tests (which ran a couple of hours for the extended test) and everything checked out fine. I don't know if this will help anyone with the same problem or not. I started testing my computer because of WiFi dropping out more than usual and decided to inspect the computer before I called Xfinity. I did not experience any other issues before I started looking for them and in all fairness to Apple, Xfinity's drop out rate in my area looks like a bad EKG. Lesson learned? Go with the easy stuff first. Thanks to everyone for providing assistance. Here's the last DriveDX test results:

https://discussions.apple.com/content/attachment/b25183b6-d649-4704-9634-d76d789128e9

To close this off, you should also inspect (feel free to post here) the health indicators for both drives. There are 17 for one of the drives, 23 for the other (the two drives that make up the fusion drive). These will show you lifetime remaining and other health indicators like temperature, errors encountered, bad blocks, etc.

The Disk Utility Disk First Aid error you received should not have anything to do with XFINITY or your internet provider. In fact, that Disk First Aid should run properly even when disconnected from WiFi and disconnected from the Internet.

Refer to another Question with similar Error Message. Different OS in play there but similar Setup - Fusion Drive

Storage system verify or repair failed 69… - Apple Community

Did you follow the steps in this article exactly?

How to repair a Mac disk with Disk Utility - Apple Support

I don’t know anything about Drive DX. You’ll have to ask them what that means.

Unless you’re having an disc related problem, the results of first aid probably don’t matter a bit.