Having similar issues as reported by separate threads. I could see that you requested us to start our own threads, so here goes:
Even though I attach a featured image via the "Featured Image" function in post creation (like I always do for all my posts), the new Jetpack version refuses to recognise it.
This goes for Publicize, which pushes out a random image from the post instead of the Featured image. This also goes for when a "Facebook" share button is pressed - I am then allowed to pick from up to 4 thumbnails, none of which are the "Featured Image".
Thanks in advance,