UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.106 Safari/537.36

Example URL:
www.youtube.com

Steps to reproduce the problem:
1. Go on Youtube and click on a playlist or a video.
2. Playlist: click the next video from that playlist multiple times
3. Autoplay: click on the next autoplay video multiple times

What is the expected behavior?
The site should load all upcoming videos from autoplay or a playlist smoothly without lagging or often even crashing!

What went wrong?
After 5 or more videos the site starts lagging when watching videos (wether i watch them until the end or click on another one) and also crashes after a while and playlists or autoplay just stop until i open the tab and refresh the site again.

Does it occur on multiple sites: No

Is it a problem with a plugin? N/A 

Did this work before? Yes I can't give an exact date, I just know that it worked normally before.

Does this work in other browsers? Yes 

Chrome version: 51.0.2704.106  Channel: stable
OS Version: 10.0
Flash Version: Shockwave Flash 22.0 r0

On my Computer there are 2 Profiles, one for me and one for my brother. On his profile youtube works normally on chrome so here are some differences i noticed:

I am logged in chrome and my gmail account data synchronizes.
My brother doesnt have extensions installed and i have the following ones installed: Adblock Plus, Browsec, Adf.ly Skipper, Proxflow