I think there is a similar Windows Forms issue for WPF.

When we try to convert WPF Diagram to SVG we encounter this exception:

System.Exception was caught
  Message=Can't convert the brush of the 'System.Windows.Media.RadialGradientBrush' type
  Source=MindFusion.Diagramming.Wpf.SvgExport
  StackTrace:
      at MindFusion.Diagramming.Wpf.Export.x0e6976d93edd8615.xbb2cbd1695471745(Brush x4c2a99b0c1203b8c, Rect xda73fcb97c77d998, Transform x678241938de24d81)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x593e8c8533662217(DrawingGroup xb5ee4eb70a91d71e, Transform x678241938de24d81, Geometry xf415bfdf81178f19, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x1d99ef2e78afcba8(Visual x81deb0c3fdb19a1b, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x39b8b9e82da61fbd(Visual x81deb0c3fdb19a1b, Transform xae720f0498ad1d42, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x1d99ef2e78afcba8(Visual x81deb0c3fdb19a1b, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x39b8b9e82da61fbd(Visual x81deb0c3fdb19a1b, Transform xae720f0498ad1d42, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x1d99ef2e78afcba8(Visual x81deb0c3fdb19a1b, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x39b8b9e82da61fbd(Visual x81deb0c3fdb19a1b, Transform xae720f0498ad1d42, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x1d99ef2e78afcba8(Visual x81deb0c3fdb19a1b, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x39b8b9e82da61fbd(Visual x81deb0c3fdb19a1b, Transform xae720f0498ad1d42, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x1d99ef2e78afcba8(Visual x81deb0c3fdb19a1b, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x39b8b9e82da61fbd(Visual x81deb0c3fdb19a1b, Transform xae720f0498ad1d42, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x1d99ef2e78afcba8(Visual x81deb0c3fdb19a1b, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x39b8b9e82da61fbd(Visual x81deb0c3fdb19a1b, Transform xae720f0498ad1d42, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x1d99ef2e78afcba8(Visual x81deb0c3fdb19a1b, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x39b8b9e82da61fbd(Visual x81deb0c3fdb19a1b, Transform xae720f0498ad1d42, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x1d99ef2e78afcba8(Visual x81deb0c3fdb19a1b, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x39b8b9e82da61fbd(Visual x81deb0c3fdb19a1b, Transform xae720f0498ad1d42, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.x593e8c8533662217(DrawingGroup xb5ee4eb70a91d71e, Transform x678241938de24d81, Geometry xf415bfdf81178f19, Geometry x382baa81329e953f)
      at MindFusion.Diagramming.Wpf.Export.SvgExporter.Export(Diagram diagram, String filePath)
      at S2T.RAHS2.Client.Views.Modeling.DiagramController.Export(ExportFormat format, String filePath) in C:\Users\Ch\Desktop\FOCSVN\ClientViews\Modeling\DiagramController\DiagramControl
ler.cs:line 393
      at S2T.RAHS2.Client.Views.Modeling.DiagramController.ExportOperation() in C:\Users\Ch\Desktop\FOCSVN\ClientViews\Modeling\DiagramController\DiagramControl
ler.Operation.cs:line 136
  InnerException:

Thank you.

Please check the version from the PM page, it should export radial gradients successfully now to SVG. We've found the other exporters do not support radial gradients too, we'll implement them there for the official release later next month.

Stoyan