If ON THE SAME page (home-test-1), if you ONLY add announcements to the category field, it does that, then it is a puzzle indeed, as all things being equal, there is no reason for the excerpt to vanish…
Two things I would try:
- Add the category name test to the posts with the category announcement, then in home-test1, add the category test instead of announcement in the category box, and see if the same thing happens.
- Next Add the category announcements to the post with the category project events, then in home-test1, add the category announcemenst to the categoty box, and see if the excerpt vanishes on all 4 posts or not.