I believe someone else posted about this but I think I can shed a little light on the problem and provide a fix. KB4103721 is a cumulative security update for Windows 10 v1803 that was just recently released. We've found that if the Remote Utilities Host service runs on startup and you install KB4103721, you won't be able to get to the login screen on boot. If you roll back the update and turn off the service on startup, install the update, and re-enable the service it works fine.
To roll back the update, we booted into "System Restore" off the UEFI boot menu which takes you to a Windows recovery and troubleshooting menu where you can either select system restore or roll back Windows.