It is confirmed that Twitter erroneously chooses the last speced og:image tag and not the first, as the OG spec explicitly says it should.
A workaround can be to add a specific twitter image tag. This has been talked about in Yoast Wordpress SEO Git repo, but is not implemented in the plugin as of now.
You should be able to do something like this in your theme header manually:
if post has featured image {
print twitter image tag with that thumbnail
}
Note: It’s not trivial to access featured image from outside the loop, and the image needs to be < 1 MB file size so you probably want to get a downsized version.
