Hi Francis,
Thank you for the details, it helps a lot!
I checked both posts, but they are not password protected, as you can see it on the editor: https://i.imgur.com/3FHhBfB.png
Both posts are publicly visible by WordPress defaults. 3rd party plugins may use different methods for password protection, but that will not work.
I usually try to recommend some custom code, but for that I need some more information. If there is a method within the plugin, which we can use to determine if the current user has access to the given post by ID – any function, class method etc.. – then I can recommend a small custom code to remove the unwanted results programmatically.