Windows 10 1903 users continue to complain that Start Menu is giving a critical error message and that Edge now will not launch after installing the latest KB4517389 cumulative update. For some, uninstalling the recent cumulative update has fixed these issues, but for others the Start Menu problem persists. Microsoft has not acknowledged any issues with this update in the Windows 10 health dashboard, but these issues are being reported in the Feedback Hub, Microsoft’s community forums, and elsewhere. If you are willing to trade a security downgrade over a functional Windows Start menu and Microsoft Edge, use the following steps to remove the update.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-1903-known-problems-in-the-kb4517389-update/