Workarounds:
- use RenderMode="Lightweight"
- OR, set DecoratedControls="All"

Repro:

			<telerik:RadFormDecorator ID="RadFormDecorator1" runat="server" DecoratedControls="Textbox,Textarea,Buttons,Scrollbars,Select,CheckBoxes,RadioButtons"
				 Skin="Default" RenderMode="Classic" />
			<div class="container body-content">
				<h2>First Application </h2>
				<p>SFSFSDF</p>

				<br />
				<asp:RadioButtonList runat="server" ID="dlSchdId" RepeatColumns="6" RepeatDirection="Horizontal"
					Width="100%">
					<asp:ListItem Text="test 1"></asp:ListItem>
					<asp:ListItem Text="test 2"></asp:ListItem>
				</asp:RadioButtonList>

				<asp:CheckBox runat="server" ID="chk1" Text="Check Box 1" />
			</div>