At work (with a firewall) youtube always turns on “disable polymer”. This means that the video starts and after a few seconds (if it is the active tab) it resets the URL with disable polymer and starts over. Also most (but not all) of the time the recommended videos on the right do not show up, that whole section is blank.
I can tell you that Polymer is the name of YouTube’s recent redesign, which is about 6 months old or so right now. And I can see from a quick Googling that adding ?disable_polymer to the URL does exactly what it implies.
I can’t tell you why your browser is doing that after a few seconds of playtime. It could be a browser extension, made by someone who doesn’t like the Polymer look (if so it could have been installed by your company automatically). It could be that YouTube is detecting some kind of error and thinks reloading without Polymer enabled will resolve it.
I also can’t tell you why the recommendations don’t work after Polymer is disabled. Sorry.
Most likely your company is running a SSL intercept and or a proxy that doesn’t work well with HTML5.
Note: If they are running an SSL intercept, or outdated proxy be careful about logging into banking or other critical services.
That’s a interesting point. Also maybe the company network is blocking WebSockets, and Polymer requires WebSockets to function-- so YouTube’s fallback is to reload with the older interface. (Just a guess, I have no idea if YT actually uses WebSockets or not.)
It may be that your employer is trying to block your access to YouTube. You might want to consider how much attention you want to draw to the fact that you’re trying to access YouTube before finding out whether or not the company has a policy against it.