I have the following issue in Safari 8.0.7 on OS X 10.10.4 when playing videos in YouTube: The video continues beyond the end of the track. The image and sound stop at the end of the video, but the timer continues to count upwards.
Here's a screenshot:
This is pretty annoying when watching a playlist with music videos. I have to manually skip to the next track when I notice that it's playing beyond the end of the track.
This works fine in other browsers, e.g. Chrome.