The connection StartCap and EndCap values are not applied when set through ConnectionDefaults.
The bug is introcuded version 2016 R3 SP1


Code to reproduce the probelem:
        <telerik:RadDiagram ID="RadDiagram2" runat="server" Skin="Windows7" Height="365" Width="1600">
            <ShapeDefaultsSettings Height="30" Width="100">
                <ContentSettings FontSize="12" />
                <FillSettings Color="#f2f2f2" />
                <StrokeSettings Width="2" />
            </ShapeDefaultsSettings>
            <LayoutSettings Enabled="true" ></LayoutSettings>
            <ShapesCollection>
                <telerik:DiagramShape Id="s1"></telerik:DiagramShape>
                <telerik:DiagramShape Id="s2"></telerik:DiagramShape>
                <telerik:DiagramShape Id="s3"></telerik:DiagramShape>
            </ShapesCollection>
            <ConnectionsCollection>
                <telerik:DiagramConnection>
                    <FromSettings ShapeId="s1" />
                    <ToSettings ShapeId="s2" />
                </telerik:DiagramConnection>
                <telerik:DiagramConnection>
                    <FromSettings ShapeId="s2" />
                    <ToSettings ShapeId="s3" />
                </telerik:DiagramConnection>
            </ConnectionsCollection>
            <ConnectionDefaultsSettings StartCap="FilledCircle" EndCap="ArrowEnd" />
        </telerik:RadDiagram>