sound too slow

Hi, Today I downloaded this video:
https://www.youtube.com/watch?v=eY1XtWyKlJA

It's a 2-hour orchestra concert. The video quality of the download is perfect, but the sound plays too slow. You can clearly hear strong artefacts while the audience is clapping at the beginning of the video (sounds really bad) and also while the orchestra is playing. Why is that? I already set everything to the highest possible quality. The downloaded file is almost 600 MB.