Microsoft June 2019 Patch Tuesday updates have caused problems in Windows 10 Event Viewer. Microsoft has created a support bulletin for this issue that states: “MMC has detected an error in a snap-in and will unload it”” Users are also reporting seeing an “”Unhandled Exception in Managed Code Snap-in”” error. The only way to fix this error is to delete the custom views that are having a problem. A workaround is provided in the article that allows you to use a. PowerShell command to access your existing custom views.”
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-v1903-v1809-updates-break-event-viewer-custom-views/