I’m adding a further update to this, because I’m having the same issue with a number of sites, all of which have been whitelisted for summary_large_image.
The first, http://judahraine.com is listed above with the problem of the image not showing in preview, even though the site is whitelisted.
My latest tweet from the site showed this:

If I click in the are marked by the red X in the image below, this is what shows:

If I click on details:

The second, judahraine.blogspot.com has been whitelisted and the correct image displayed in image preview. However, my latest tweet shows:

The same results as for judahraine.com result if I follow those steps.
Interestingly enough: I just ran the validator again, and the image preview is no longer pulling the large image. I get exactly the same result as for the validator on judahraine.com, i.e. my profile picture and site description. The image pulled through absolutely fine yesterday, and I have made no changes to the site at all aside from adding a post.
The third, http://truthimmutable.com, has been whitelisted and the correct image showed in validator.
The site posts automatically, and this shows up perfectly in the twitter feed for truth immutable:

However, if I share from the site as a visitor, it displays:

If I click on details it then displays the full image.
I’ve taken the time to add all of these as it highlights a particularly strange collection of anomalies:
First, the twitter meta tags used for all are identical, except for the individual site information.
Second, the validator appears to ‘change its mind’, i.e. what showed in yesterday’s validator is different to the one run today.
Third, A site posts differently ‘second time around’, even though it’s using exactly the same meta tags and information.
There has to be a rational explanation for this. I’ve done extensive research in innumerable forums, and have also picked up that these seem to be a common problems as per posts on this forum.
While I hesitate to be a pest, I’m sure that there must be a way to resolve this. I can find no other way to contact support except via these forums, and so I have no choice but to persist until I can find answers, having spent almost two days already trying to rectify this issue without assistance.
I would be very grateful for your input, thank you.