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>

When more than one shapes have HTML content containing image with the same path, only the image inside the first shape is rendered:
https://www.screencast.com/t/mYJVfSOlP


Code to reproduce:
        <telerik:RadDiagram runat="server" ID="RadDiagram1">
            <LayoutSettings Enabled="true" Type="Tree" Subtype="Right" />
            <ShapesCollection>
                <telerik:DiagramShape Id="s1" >
                    <ContentSettings Html="<div>Shape 1</div><img src='sampleImage.png' />" />
                </telerik:DiagramShape>
                 <telerik:DiagramShape Id="s2" >
                    <ContentSettings Html="<div>Shape 2</div><img src='sampleImage.png' />" />
                </telerik:DiagramShape>
            </ShapesCollection>
        </telerik:RadDiagram>

When you use the ConnectionDataSource of RadDiagram to data bind an SqlDataSource to its connections, a NullReferenceException is thrown.

You can avoid this issue by using ConnectionDataSourceId instead.

RadDiagram throws a NullReferenceException when you bind it declaratively and place it in the ItemTemplate of a data bound control, for example a Repeater.

When you change the beginning or the end of an existing RadDiagram connection and call the client-side save() method, the exported data for the modified connection will not be updated.

Does not matter what value is set to the Connection's StartCap/EndCap properties, the ends of the connection are rendered as if the value of these properties is "None".