The issue is reproducible in Standalone Report Designer which internally uses RadRibbonWindow. When the Auto-hide taskbar feature in Windows is enabled and the window is initially maximized, the RadRibbonWindow position is not correctly calculated and looks offset. Here's the corresponding issue in Progress® Telerik® UI for WPF Feedback Portal: RibbonWindow: The window is clipped when maximized initially and OS taskbar is auto-hiding.