I finally got a chance to try again this morning. Ran the stand-alone installer for KB4490628 (SSU) first and that installed no problem. Then I tried KB4474419 again and had the same result as before, failed to install and reverted on reboot. Then I ran sfc /scannow again and extracted the CBS.log file to Desktop. Third line from the bottom: 2019-03-16 06:04:19, Info CSI 00000348 [SR] Repairing 0 components Any ideas what to try next?