Have seen the same problem..i don't know if it relates to sites using cloudflare & this https://blog.cloudflare.com/introducing-universal-ssl/ .see if the ssl certificates comes from cloudflare.
Posts made by galileo
RE: Unable to verify the website's identity (OCSP error)Opera for Windows
RE: OpenSSL in Opera 12.16Opera for Windows
Andreas Bovens, Extensions product manager & developer relations lead at Opera Software said there is no problem with the bug, see https://twitter.com/andreasbovens/statuses/454004623301672960