Ah, I think I know what happened.
In the latest GP we started making use of post formats – if your post have anything other than the standard post format set, they will display the full post (so images etc.. will be shown).
Another thing that changed is that if you use the More tag (https://en.support.wordpress.com/splitting-content/more-tag/) it will display formatted content (including images) up until that tag is reached. This allows people to display most of their posts as an excerpt (if that setting is set), but still show formatting in some posts if necessary.
Let me know if either of these scenarios ring true.
Sorry for the inconvenience! Hopefully these features are useful in the future.