Issue: Facebook OpenGraph doesn’t diplay the image set into the og:image meta and pick another one instead.
It seems to be an issue with https URL in open graph. There is a closed bug report in facebook without answer from facebook.
Some people in stackoverflow have found a work around.
Work around 1: upload all your picture in a non https domain and use these URL for your og:image content property.
Work around 2: use og:image:secure_url and use the facebook sharing debugger to lint your page. https://developers.facebook.com/tools/debug/ [Work around currently in test]