Search engines not using content from og:description - WordPress related?

I just cannot figure this out... if I've deliberately placed an "og;description" meta tag in the header just so that search engines will use that exact content in their search result description of a website, why would they ever override this explicit instruction and just pull some other bullshit in that it read off the page? That is, unless I'm just a complete dumbfuck and something I've done wrong with WordPress is causing this and it's my own mistake. Are search engines honestly overriding website owner's own title and description field in search results? Is this shit normal?