ENVIRONMENT and STATS
I am playing one video, even no other tabs are open. 
https://www.youtube.com/watch?v=UdBMTyZn_tw
when navigating to another video, last opened video is playing in the background.

and In network tabs, I can see the last socket connection is also established.

REPRO STEPS

play one video navigate to another sometimes it will come.

https://www.youtube.com/watch?v=UdBMTyZn_tw

play this and close the tab again open the same link you will get the last played, still playing in the background.

You can see two video ids for XHR.

1.https://r15---sn-h557snee.googlevideo.com/videoplayback?dur=331.799&ip=182.76.20.30&clen=14162426&ipbits=0&gir=yes&itag=243&ei=1U90WdXmJofkogOnyJ9g&sparams=clen,dur,ei,expire,gir,id,ip,ipbits,itag,keepalive,lmt,mime,mm,mn,ms,mv,pl,requiressl,source&id=o-ADWCExaAjr9KthEk5Q-nydyBPMuxPCVKK-sENXXJ7yln&signature=0EA62B9349DA1EB9A189656978C4C123CA3DA913.03A0C75B1287F0314EC504126A252B006F5B25AF&source=youtube&pl=22&mime=video%2Fwebm&key=cms1&lmt=1493003296349628&requiressl=yes&keepalive=yes&expire=1500816437&alr=yes&ratebypass=yes&cpn=U2ybib5prf6D_pT5&c=WEB&cver=1.20170720&redirect_counter=1&cms_redirect=yes&mm=30&mn=sn-h557snee&ms=nxu&mt=1500794745&mv=m&range=7775695-9299959&rn=29&rbuf=92452

2.https://r15---sn-h557snee.googlevideo.com/videoplayback?dur=331.841&ip=182.76.20.30&clen=5547474&ipbits=0&gir=yes&itag=251&ei=1U90WdXmJofkogOnyJ9g&sparams=clen,dur,ei,expire,gir,id,ip,ipbits,itag,keepalive,lmt,mime,mm,mn,ms,mv,pl,requiressl,source&id=o-ADWCExaAjr9KthEk5Q-nydyBPMuxPCVKK-sENXXJ7yln&signature=4E03BCCC3B56B0DEF9C2241DD138C29CDBFEE876.3A3338BB44BEF841511AC9B5D139BBE1631E2162&source=youtube&pl=22&mime=audio%2Fwebm&key=cms1&lmt=1492997677943792&requiressl=yes&keepalive=yes&expire=1500816437&alr=yes&ratebypass=yes&cpn=U2ybib5prf6D_pT5&c=WEB&cver=1.20170720&redirect_counter=1&cms_redirect=yes&mm=30&mn=sn-h557snee&ms=nxu&mt=1500794862&mv=m&range=3198483-3528277&rn=30&rbuf=102549

ACTUAL RESULTS
It should play one at a time.

EXPECTED RESULTS


ADDITIONAL INFO
Anything else which may help us debug the issue; screenshots of error
messages or states are always helpful.

 

Deleted: video error.png 1.0 MB

	video error.png 1.0 MB View Download