When Gutenberg is enabled I am seeing an issue where the post slug field is not saved, specifically it is cleared out entirely, when a post is saved with a custom status. I have traced done this issue to this code - https://github.com/Automattic/Edit-Flow/blob/0.9/modules/custom-status/custom-status.php#L1395-L1431. It appears that since the $_POST['post_name'] element is not set when editing a post in Gutenberg, the function always thinks the user did not set a custom slug, and therefore it clears the post slug.
I have done some rough testing and I believe this logic can be removed entirely since the custom post status API has been updated over the years to better support custom post slugs.