Issue is non-reproducible with the latest version of ArcGIS Maps SDK for .NET version 200.2.
Download the latest version of ArcGIS Maps SDK and retry the workflow.
Here are some of the useful links and resources for reference:
What's new in 200.2 - https://developers.arcgis.com/net/release-notes/release-notes-for-200-2/
Latest documentation: at https://developers.arcgis.com/net/maps-2d/wraparound-maps/
Latest GeometryEditor sample: https://github.com/Esri/arcgis-maps-sdk-dotnet-samples/tree/main/src/WPF/WPF.Viewer/Samples/GraphicsOverlay/CreateAndEditGeometries
If any issues persist with the latest version of ArcGIS Maps SDK, contact Support Services for further assistance.