What is the problem of downloading youtube video in iframe?

Question

YouTube

I copy the code from YouTube, the bottom line is that the video of 1 frame is displayed without problems:

<iframe width="560" height="315" src="https://www.youtube.com/embed/Q_NB5luxtic" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

and video 2 frames gives an error:

<iframe width="560" height="315" src="https://www.youtube.com/embed/E53eiN1VJo8" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

Yes, and in principle, the video is loaded every other time.

Answer 1

https://jsfiddle.net/ujsa7d0g/
At the moment everything is working.
1. YouTube servers are overloaded. (typical for evenings and weekends)
2. Browser errors. (especially typical for firefox)
3. CMS error.
4. Errors in the code that create display problems.