Editing timestamp not working after update

Hi. I did the latest update from version 8.9.4 to 8.9.6. Thankfully, I kept the backup of the old CT folder before doing that. Now I’m running again 8.9.4. Why? Well, I have a daily need, that is to change the listings timestamps manually from the admin area. And could not do it anymore after the update. When I pressed the Edit button beside Scheduling, noting would happen. Only the URL would change into someting with https://….action=edit#edit_timestamp , but the action would not happen. Changed the CT manually back to 8.9.4 (the only thing I did) and now it works. So no update for me. Any idea how can this be fixed (and why it happened?)?