I have looked around, but I haven’t found any solution.
I have cards validated for my site (http://sobrebitcoin.com/) and I don’t get any errors or warnings when I preview the card. The link works just fine and bring to the right post, but the rest is wrong. Picture and summary is from a different post. Each time a different one, just a random one from the site.
E,g, The card for http://sobrebitcoin.com/2015/03/16/5-alternativas-a-ebay-usando-bitcoins/ shows the picture and summary of http://sobrebitcoin.com/2015/02/05/ross-ulbricht-declarado-culpable-en-el-juicio-sobre-silk-road/.
I’ve activated/deactivated SEO by Yoast and JM Twitter Cards but I got the same results for both of them.