Tried that twice and didn't fix it.Have you tried trashing the Finder's plist?
Just installed El Capitan, so far everything seems butter smooth except this thing with the sidebar Guess theres no fix for it except waiting for another update. ...downgrading to yosemite is at least not an option, since everything else seems better and faster. Like getting a new machine really.
Send feedback! don't just wait.. SEND FEEDBACK.. or it won't get fixed.