1809 update fails with 0x800F081F error

I downloaded MediaCreationTool1809.exe and used it to create an installation thumb drive for Win10 x64 1809. I used the thumb drive to update my laptop to 1809 (running setup.exe off the root of the thumb drive), and that completed without problem. After a couple of days without problems on the laptop, I used the thumb drive to update my desktop via the same process, but after performing the initial part of the update, and then rebooting to continue it, setup eventually came back with a window titled "Windows 10 Setup" and containing the text:

We couldn't install Windows 10
We've set your PC back to the way it was just before you started installing Windows 10
0x800F081F - 0x20003
The installation failed in the SAFE_OS phase with an error during INSTALL_UPDATES operation

A bit of googling showed a couple of possible causes for the problem, but they don't seem applicable - I'm not using 3rd party antivirus, and C: has sufficient free space (~35Gb free). Any suggestions on a fix?

Well, running SetupDiag seemed to indicate that the problem was with Windows Developer Mode:

Error: SetupDiag reports DISM add package failure.
DISM Error: 0x800f081f
Package = Add [1] package C:\$WINDOWS.~BT\DUImageSandbox\Microsoft-OneCore-DeveloperMode-Desktop-Package~31bf3856ad364e35~amd64~~.cabAdd Package Error: 0x800F081F

So I disabled Developer Mode and uninstalled the Developer Mode app, rebooted, restarted the install, and it completed successfully.