When the modules are removed from the code behind, the editor's content are is set with higher height value, than expected. This causes the editor's layout to break. 

Possible resolution is to attach a custom Client-side function on the OnClientLoad event of the editor, which invokes the onParentNodeChanged() method. Please follow the following example setup:

<telerik:RadEditor ID="PageContent" runat="server" OnClientLoad="OnClientLoad">
</telerik:RadEditor>

<script type="text/javascript">
	function OnClientLoad(editor, args) {
		editor.onParentNodeChanged();
	}
</script>