Am I wrong, or was it possible, before, when you wanted to edit your post (or edit someone else's post when you are an admin), to modify the post title?
It seems, now, that you don't have this possibility...
It seems you have the same issue as described here: https://wpforo.com/community/how-to-and-troubleshooting-2/cant-edit-topic-title-in-post-moderation-edit-mode-anymore/#post-41510
If so, please follow the solution provided in the post.
You're right, it's solved now.
Thank you so much!