If you wish to record a new video of the scaffold model which already has a video attached to it, you will need to remove the existing video link.
To do this:
In the top-right, click YouTube Video and select Remove Link to Video.
This will allow you to record a new video of the 3D model. Recording and uploading a new video will not replace the original video on YouTube even if the title is the same.
Note: To delete a video, go to your YouTube page where the videos are hosted.