This issue is not reproducible using the new GeometryEditor available in ArcGIS Maps SDK for .NET. Upgrade to the latest version of ArcGIS Maps SDK for .NET. If the issue continues to affect the work in a supported release, contact Esri Support Services. To see what's new in the latest version of ArcGIS Maps SDK for .NET, refer to: https://developers.arcgis.com/net/release-notes.