In OBS, use the following settings to ensure full playback of a prerecorded video on your live broadcast.
To change your pre-recorded video’s settings, right-click on the video and click Properties. Now, checkmark Loop, Restart playback, and Hide source, and press OK.
Now, when you transition to the pre-rerecorded video, your video becomes active and it restarts playback. That way, you’ll capture the entirety of the video.