facebook share

i really tried, but i can’t seem to find this particular problem among the support topics. anyway, the problem is the facebook share: unlike the twitter share (which works fine), i can’t share the post with the facebook. in chrome, it throws an error, and in firefox it always points to the login page (sometimes it does that too in chrome).
obviously, the whole site is “protected”, using your social login for users.
i’ve checked with facebook debug tool, and i cant’ see a problem there. i’ve sorted the opengraph problems on the website, but facebook share (in the best case scenario) keeps redirecting to the (custom) login page. is there a way to circumvent that?