Thanks for your quick reply, @iclyde,
I tried all of these things, but none solved the problem However, after looking more into it, I realized the problem is caused by custom PHP code inside the functions.php file to show sticky posts above the rest of the posts on archive pages. When I delete that piece of code, the widget doesn’t show the sticky post anymore (as desired).
I’ll mark the topic as resolved since it’s not a bug in the plugin, but rather a template issue from my side. Thank you for your time, @iclyde!