For the time being you can use the following workaround:
ASPX:
		<div style="border: 1px solid red; height: 300px; width: 400px; overflow: scroll;">
			<div style="border: 1px solid green; height: 500px; width: 200px;">
				<telerik:RadDockZone ID="RadDockZone1" runat="server" RenderMode="Lightweight">
					<telerik:RadDock ID="RadDock1" runat="server" Resizable="true" RenderMode="Lightweight">
						<ContentTemplate>
							<div style="border: 1px solid blue; height: 100px;"></div>
						</ContentTemplate>
					</telerik:RadDock>
				</telerik:RadDockZone>
			</div>
		</div>
		<script>
			var Browser = Telerik.Web.Browser;
			$ = $telerik.$;
			Telerik.Web.UI.RadDock.prototype._initResizableWidget = function()
			{

				if(this._resizableWidget && this._resizableWidget.dispose)
					this._resizableWidget.dispose();

				if(!this._resizable) return;

				if(Browser.webkit) {
					//need to kickstart the css transform, because of a quirk in the layout engine of webkit/blink when it comes to position:static inside position:relative
					this._kickStartCssTransform();
				}

				this._resizableWidget = new Telerik.Web.UI.Widgets.Resizable(this._element, {
					handles: this._getAvailableHandles(), appendHandleToElement: true
				});

				if(this._renderingView)
					this._setResizeLimit();

				if(this._collapsed)
					this._resizableWidget.hideHandles();

				this._resizableWidget.add_resizeStart($.proxy(this._resizeStartHandler,this));
				this._resizableWidget.add_resizing($.proxy(this._resizingHandler, this));
				this._resizableWidget.add_resizeEnd($.proxy(this._resizeEndHandler, this));
			}
		</script>

RadDockLayout cannot persists its state if contains more than 9 docks.

Code to reproduce (if one of RadDocks is removed the state will be persisted properly):

            <telerik:RadDockLayout runat="server" ID="RadDockLayout1" EnableLayoutPersistence="true" RenderingMode="Lightweight"
                LayoutPersistenceRepositoryType="Cookies" LayoutRepositoryID="repID20210406_1">
                <telerik:RadDock RenderMode="Lightweight" ID="RadDock1" runat="server"
                    UniqueName="RadDock1" AutoPostBack="true">
                    <ContentTemplate>
                        dock 1
                    </ContentTemplate>
                </telerik:RadDock>
                <telerik:RadDock RenderMode="Lightweight" ID="RadDock2" runat="server"
                    UniqueName="RadDock2" AutoPostBack="true">
                    <ContentTemplate>
                        dock 2
                    </ContentTemplate>
                </telerik:RadDock>
                <telerik:RadDock RenderMode="Lightweight" ID="RadDock3" runat="server"
                    UniqueName="RadDock3" AutoPostBack="true">
                    <ContentTemplate>
                        dock 3
                    </ContentTemplate>
                </telerik:RadDock>
                <telerik:RadDock RenderMode="Lightweight" ID="RadDock4" runat="server"
                    UniqueName="RadDock4" AutoPostBack="true">
                    <ContentTemplate>
                        dock 4
                    </ContentTemplate>
                </telerik:RadDock>
                <telerik:RadDock RenderMode="Lightweight" ID="RadDock5" runat="server"
                    UniqueName="RadDock5" AutoPostBack="true">
                    <ContentTemplate>
                        dock 5
                    </ContentTemplate>
                </telerik:RadDock>
                <telerik:RadDock RenderMode="Lightweight" ID="RadDock6" runat="server"
                    UniqueName="RadDock6" AutoPostBack="true">
                    <ContentTemplate>
                        dock 6
                    </ContentTemplate>
                </telerik:RadDock>
                <telerik:RadDock RenderMode="Lightweight" ID="RadDock7" runat="server"
                    UniqueName="RadDock7" AutoPostBack="true">
                    <ContentTemplate>
                        dock 7
                    </ContentTemplate>
                </telerik:RadDock>
                <telerik:RadDock RenderMode="Lightweight" ID="RadDock8" runat="server"
                    UniqueName="RadDock8" AutoPostBack="true">
                    <ContentTemplate>
                        dock 8
                    </ContentTemplate>
                </telerik:RadDock>
                <telerik:RadDock RenderMode="Lightweight" ID="RadDock9" runat="server"
                    UniqueName="RadDock9" AutoPostBack="true">
                    <ContentTemplate>
                        dock 9
                    </ContentTemplate>
                </telerik:RadDock>

                <%--The state will be persisted of you comment the dock below--%>
                <telerik:RadDock RenderMode="Lightweight" ID="RadDock10" runat="server"
                    UniqueName="RadDock10" AutoPostBack="true">
                    <ContentTemplate>
                        dock 10
                    </ContentTemplate>
                </telerik:RadDock>

            </telerik:RadDockLayout>

When some content is entered in a RadDock, the project is closed, opened again and new elements are added in the content via the Visual Studio's designer, the elements that are included after the reloading of the project will disappear from the designer, after editing the dock.

It should not be possible to add docks in a RadDockZone, the property AllowedDocks of which does not include the IDs of the included docks.

I'm brand new to Telerik controls, so I know I'm not doing something right.  I have a RadDock whose ContentTemplate contains a UserControl containing a RadListBox.  The controls contained in the ItemTemplate do not appear.  I believe I"ve narrowed down the issue to the attached code.  Can you tell me why the RadListBox content does not appear?  In the code sample I have the exact same code outside of the RadDock and it displays fine.   Also, I have the exact same problem when adding my UserControl to a RadSlidingPane. The contained listbox again does no appear.
Thanks for your help,
Chris

The RadDock control cannot be expanded when it is set in lightweight render mode and its property Collapsed is set to true.

You can avoid this issue by setting the dock in collapsed state via its client-side API:

<script type="text/javascript">
    function OnClientInitialize(sender, args) {
        sender.set_collapsed(true);
    }
</script>
<telerik:RadDock runat="server" ID="RadDock1" OnClientInitialize="OnClientInitialize">
</telerik:RadDock>

The animation of the RadDock control is causes performance issues under IE8 and due to that the expanding/collapsing and the docking/undocking functionalities are not working as expected.

Disabling the animation resolves the issue: 
EnableAnimation="false"

We have this client reporting to me that RadDock control is not working on Windows 8 using Google Chrome most updated version. I have double check on this but it is working on my end using Windows 7 Google Chrome most updated version too.

She is saying that on Windows 8 Google Chrome, she would not able to drag the RadDock control from RadDockZone1 to RadDockZone2.

Let me know if this something that is a bug on your end?

Thanks,

When the content container of RadDock is configured to be a drag handle via the following code

dock.set_handle(dock.get_contentContainer());

a JavaScript error will be thrown if you call the 'clone' client-side function of the control

dock.clone()

When the browser or the page, on which a RadDock is placed, is configured with a culture that uses comma-separated values and you set the Width, Height, Top, Left properties with such a value, an exception will be thrown.

The rounded corners of RadDock controls that are using the Silk or Glow skin cannot be disabled.

When you place a resizable RadDock control (Resizable="true") in a RadDockZone without specified size and you close the dock, a JavaScript error is thrown.

When you dock a resizable RadDock (Resizable="true") in a RadDockZone, its drag handle is displaced in Chrome, which prevents you from resizing it when there are multiple docked docks.

When there is a RadDock with one or more disabled commands, you focus the dock and you use one of the default keyboard shortcuts for the disabled command(s), the keydown browser event will be disabled.

The default shortcuts are:

    ESC - Close command
    Ctrl + F11 - Toggle Expand / Collapse command
    Crtr + F12- Toggle Pin / UnPin command

As of Q1 2016 the elasticity of RadDock is not behaving properly due to  some fixed font styles like:
.RadDock .rdCommandButton
 {
     font-size: 16px;
 }

Possible workaround:
div.RadDock .rdCommandButton
 {
     font-size: 1.2em;
 }

The size of a dock is increased a bit each time it is dropped and the  EnableAnimation="True".

Video: https://www.screencast.com/t/LoUJbAb8c

Workaround:
Set EnableAnimation="False"

Steps to reproduce:
1. Run the following code.
2. Swipe the first and second dock several times (Test 1 and Test 2)

                <telerik:RadDockZone ID="Zone1" runat="server" Height="500px" Orientation="Horizontal" Width="400px">
                    <telerik:RadDock RenderMode="Lightweight" runat="server" Height="110px" Width="140px" ID="RadDock1" Title="RadDock A" DefaultCommands="None" DockMode="Docked"
                        EnableAnimation="True" EnableRoundedCorners="True" Skin="Silk">
                        <ContentTemplate>
                            <div style="background-color: blue; width: 110px; color: white">
                                Test 1
                            </div>
                        </ContentTemplate>
                    </telerik:RadDock>
                    <telerik:RadDock RenderMode="Lightweight" runat="server" Height="110px" Width="140px" ID="RadDock2" Title="RadDock B"
                        DefaultCommands="None" DockMode="Docked" EnableAnimation="True" EnableRoundedCorners="True" Skin="Web20">
                        <ContentTemplate>
                            <div style="background-color: red; width: 110px; color: white">
                                Test 2
                            </div>
                        </ContentTemplate>
                    </telerik:RadDock>
                    <telerik:RadDock RenderMode="Lightweight" runat="server" Height="110px" Width="140px" ID="RadDock3"
                        Title="RadDock C" DefaultCommands="None" DockMode="Docked" EnableAnimation="True" EnableRoundedCorners="True" Skin="Web20">
                        <ContentTemplate>
                            <div style="background-color: green; width: 110px; color: white">
                                Original
                            </div>
                        </ContentTemplate>
                    </telerik:RadDock>
                </telerik:RadDockZone>


Result: The width of the first two docks is different than the one which has not been dragged (Original)

Expected: The width of all docks remains the same.