Not sure if this is a bug or not, but I have added a Category Page with Intro (Tempera Theme) and the post excerpts show up fine, but the share icons have a little generic placeholder image instead of their correct social image. The share icons display properly in the full post page. Have cleared all cache and checked in 4 browsers.
The category page with intro is technically a page. If you’ve turned off Jetpack’s sharing functionality on pages the buttons will still show up in the posts in the list, but will be missing the icosn. To resolve this, re-enable sharing on pages.