To make navigation easy, especially for a long video, the CC-segment and wave graph is wider than the browser window. This allowas sophisticated navigation tasks. So it looks good at the first run:

But in case I try to drag'n'drop the video scroll bar a second scroll bar shows up, the browser scroll bar and interference with the first video scroll bar due to overlapping:

Drag'n'drop the video scroll bar to navigate in the video is nearly not possible due to a really narrow area of the scroll bar!