This happens because streamed videos behave differently from embedded videos in autoplay:
- Streamed videos (link from Youtube): The video plays as long as it lasts, and it overrides the length of autoplay time intervals.
Embedded videos (uploaded from your computer): Autoplay cuts the videos, and they will play only for the duration of the time set for autoplay.
Note: If you would like your videos to start playing automatically during your presentation, please add the video itself to your path (and not to the frame around it). For more details, please see Can my video start automatically? (FAQ)