youtube video loads in header way out of proportion

It used to work, that my youtube video would run in the header of my main page and loop. Then around six months ago, it was suddenly way out of proportion. No CSS width=100%, height=auto works..

Are you going to fix this?

I took it off my page because I don’t want it looking crazy, but a quick Google search will show that this has been an issue for awhile.. but the latest CSS fix on github is not working.