We just got our "second Tuesday" updates (12/12/2017) on our W10 machine running V1709.
The cumulative update KB4054517 failed with an error code of 0x80070643.
The only thing we've discovered so far is that this machine will not display our other 3 PC's on the network when we select "Network" in File Explorer. But all three other PC's can "see" and access this PC no problem. And we ran a batch backup job on the affected PC and it was able to copy files from all three other PC's. So it's just a display problem in File Explorer -> Network.
We've run Windows Update Troubleshooter and told it to Apply Fixes whenever it prompted us, and it DID report that it found and fixed three issues:
Potential Windows Update Database Error - Fixed
Windows Update Component Must Be Repaired - Fixed
Check for pending updates - Fixed
After exiting the Troubleshooter, we clicked on "Check for Updates" again and it said "Your device is up to date".
We noticed that the build number after the "failed" update had changed to 16299.125. So the system thinks it DID install something newer than it had before, but Windows Update thinks the cumulative patch failed to install.
BTW, the other "Second Tuesday" patches (Adobe Flash KB4053577 and Windows Malicious Software Removal Tool KB890830) both installed OK.