When right clicking on a control near the bottom of the screen, the context menu (implemented as a RadContextMenu) opens downwards from the point where the mouse was clicked. This results in the majority of the menu going off the bottom of the screen.

On subsequent right clicks in the same area, the context menu opens upwards from the click position, which is correct functionality as the menu is not obscured.

The menu is shown by calling:
contextMenu.Show(viewerControl, e.Location);

The bug occurs the first time that the context menu is shown on a control.