When you try to copy and paste RadSplitContainer from one form to another, it loses its child panels and if it contains any other child controls, they become children of the form.
The issue is duplicated with another item and both feedback items are merge into - FIX. RadSplitContainer - cut/copy and paste RadSplitContainer from one form to another, it loses its child panels and controls. Here is the link: http://feedback.telerik.com/Project/154/Feedback/Details/109931-fix-radsplitcontainer-cut-copy-and-paste-radsplitcontainer-from-one-form-to-an