Custom slide title no longer working

The Slide Title option isn’t working anymore. Putting text where says “custom title for slide made from this post” in the slide settings in post editor no longer keeps the text I put there. It reverts to the post title as entered on the main post.

Up until a couple months ago, that was working fine. Was something changed in a recent update? Please fix, or let me know how I can override this behavior.

Thank you!