When a menu popup is opened with a shortcut its location is initially not correct. If you open the menu by clicking on it its location will be correct. If you then move the form containing the menu and use the shortcut again the location will be the last location of the menu item opened by mouse click.

When a split button is in the command bar and you click on the action part the location of the popup is initially not correct. If you click on the arrow part the location will be correct and after that if you click on the action part the popup location will be again correct. If you move the form containing the command bar, containing the split button and click on the action part location of the popup will be the last location of the popup opened by arrow part click.