"analyze the core of a problem" - that's a good one!!!
I never wanted to spend any time on this but I got sucked in out of necessity. I have no time, especially to reinstall the OS. Eventually, I would have tried updating to Monterey and prayed that would succeed. I could talk software engineering with you forever since I was a software engineer for decades and have combed through more logs more than anyone ever wants to. But - great idea.
Before logging out, I thought I would try Software Update one last time since it had worked ten times in a row and I was hopeful. But this time it stuck. So I left it running and restarted. It worked. I quit the Preference Pane and ran it again. It worked. Well I'm better off than I was.
I grabbed some lines out of the system.log. Most of the Software Update segments look like the following and unfortunately don't help me (other unrelated errors are similarly reported). Certificate appears on one line a few times and I included a sample of that too. I am logging out for good for awhile but I'll check back when I can.
May 20 04:32:36 supercomputer suhelperd[483]: objc[483]: Class SUReachabilityMonitor is implemented in both /System/Library/PrivateFrameworks/SoftwareUpdate.framework/Versions/A/SoftwareUpdate and /System/Library/CoreServices/Software Update.app/Contents/Resources/suhelperd. One of the two will be used. Which one is undefined.
May 20 04:32:36 supercomputer suhelperd[483]: objc[483]: Class SUPrinterScan is implemented in both /System/Library/PrivateFrameworks/SoftwareUpdate.framework/Versions/A/SoftwareUpdate and /System/Library/CoreServices/Software Update.app/Contents/Resources/suhelperd. One of the two will be used. Which one is undefined.
May 20 04:32:36 supercomputer suhelperd[483]: objc[483]: Class SUSignedFlatPkg is implemented in both /System/Library/PrivateFrameworks/SoftwareUpdate.framework/Versions/A/SoftwareUpdate and /System/Library/CoreServices/Software Update.app/Contents/Resources/suhelperd. One of the two will be used. Which one is undefined.
May 20 04:32:36 supercomputer suhelperd[483]: objc[483]: Class SUPowerAssertionManager is implemented in both /System/Library/PrivateFrameworks/SoftwareUpdate.framework/Versions/A/SoftwareUpdate and /System/Library/CoreServices/Software Update.app/Contents/Resources/suhelperd. One of the two will be used. Which one is undefined.
May 20 04:32:36 supercomputer suhelperd[483]: objc[483]: Class SUPowerSourceMonitor is implemented in both /System/Library/PrivateFrameworks/SoftwareUpdate.framework/Versions/A/SoftwareUpdate and /System/Library/CoreServices/Software Update.app/Contents/Resources/suhelperd. One of the two will be used. Which one is undefined.
May 20 04:32:36 supercomputer suhelperd[483]: objc[483]: Class SUURLConnection is implemented in both /System/Library/PrivateFrameworks/SoftwareUpdate.framework/Versions/A/SoftwareUpdate and /System/Library/CoreServices/Software Update.app/Contents/Resources/suhelperd. One of the two will be used. Which one is undefined.
May 20 04:32:36 supercomputer suhelperd[483]: objc[483]: Class KeychainMasterHandler is implemented in both /usr/lib/libIASAuthReboot.dylib and /System/Library/CoreServices/Software Update.app/Contents/Resources/suhelperd. One of the two will be used. Which one is undefined.
May 20 02:16:26 supercomputer akd[425]: objc[425]: Class AKCarrierBundlePhoneCertificate is implemented in both