To reproduce: - Add RadDock to a blank form and dock a tool window to the bottom. - Add RadRichTextBox to the tool window and set its anchor property to all for sides. - Save and close the form. - Reopen the form, you will notice that the RadRichtextBox has different size.
We do have this case already logged. Please use the following link instead: http://feedback.telerik.com/Project/154/Feedback/Details/109863-fix-anchoring-property-incorrectly-resizes-controls-at-design-time.