rendering problem is when minimized only

When the attached TextOptions.TextFormattingMode="Display" property is set to the RadWindow the window stops auto resizing its size according to the size of its content.

Maximizing RadWindow from the header button shows a window with the size of the content if SizeToContent = true. If you maximize with double click on header it is ok.

As a workaround you can set:  window.CaptionHeight= 0;

It can be reproduced with the Show method of the window or with Dock, ToolWindows and the save - load functionality.

If a ContentControl is placed inside the control and the ResizeMode is set to NoResize the SizeToContent doesn't take effect.

As a workaround all you need to do is set the ResizeMode to NoResize in the Loaded event of the ContentControl.

Currently the template of the dialogs should be customized:
http://www.telerik.com/community/code-library/wpf/window/how-to-modify-the-alert-dialog-icon.aspx

Available in the 2016 Q1 Release: Added an IconTemplate property that provides an easier way to change the predefined dialogs' exclamation/question mark images.

PreviewClosed event is called twice when using custom close button in DialogWindow

Available in the 2015 Q3 Release.

Available with the R3 2016 SP1 release. 

The Window doesn't resize correctly when dragged from the primary monitor (with taskbar) and docked to the top of the screen of a secondary monitor (no taskbar) in order to maximize it and "Show window contents while dragging" Windows system setting is disabled.

The header buttons elements are not on the proper places when the window is on a monitor with different DPI. To reproduce this the DPI of the monitors should be different for example 125% (main) and 150% (secondary). Also, to reproduce this you will need to enable the DPI awareness of the application by setting the dpiAware and dpiAwareness settings in the app.manifest file.

When the Window is opening or resizing and Winforms controls are placed inside its content the content flickers.

This happens when RadWindowInteropHelper.AllowTransparency is set to False and RadWindow is implemented as UserControl. The Window need to be maximized firstly on the main screen and then on the secondary in order for issue to be reproduced.

The issue also affects the ToolWindow that RadDocking uses for its floating Pane. In order to reproduce the problem, the primary monitor needs to have its DPI higher than the secondary one.