Use the Swap with Marker button in the Segment or Gap options to swap two markers that may have been swapped because of occlusion.
Do one of the following to select the swapping method from the Insert menu in the Label pane:
Select a marker in the Viewer window or from the Marker list in the Label pane.
In the Optical editor, move the Timeline indicator to where you want the swapping to begin or end (if you are not swapping the entire take).
Click Swap with Marker and, in the Viewer window, click on the second marker that you want to swap.
A dialog box appears asking if you are sure you want to swap the data segments of the two selected markers.
Optical dialog box
Click Ok to swap the two markers or click Cancel to abort swapping.