This issue is not reproducible with the latest version of the ArcGIS Maps SDK for .NET version 200.3. It is recommended to upgrade to the latest version of ArcGIS Maps SDK for .NET. If the issue continues to affect any work in a supported release, please contact Esri Technical Support. To see what is new in the latest version of ArcGIS Maps SDK for .NET refer to https://developers.arcgis.com/net/release-notes/release-notes-for-200-3/.