This is quite common. Check out the pages where Google found the problem. They are likely okay and Google just couldn’t crawl the CSS for some reason and therefore the page breaks visually. If you have confirmed, that the pages are actually okay, just click “Validate fix” for each error and Google will crawl the pages again and hopefully get it right this time. Of course, if you also see the same problem as Google, you need to actually fix the page first.