We've noticed what must be a bug in the RadPanelBar, sometimes it seems like the Designer does not update the ContentTemplate, but instead simply adds another ContentTemplate to the markup code, after the previous one. We noticed this bug when we could never see any of the changes we made to a RadPanelBar (it contained just text which was edited), and when we examined the HTML markup, we noticed that there were 2 ContentTemplates, one with the new text and one with the old. Removing the one with the old solved the problem.