Actually this is not a bug, rather a feature which allows users to search within categories or with the Department, Country, etc permalinks with keywords.
I did release 8.5.29 which did always search from the directory root but that broke the search for many other sites that were using it this way to allow their users to finely filter the results. So, I’ll have to revert this change this week.
I believe what you can do is add
force_home=true to your existing shortcode on this page and you’ll get the results you are seeking. It is not it’s intended purpose but I think with your setup it’ll make it work just fine.
After I release 8.5.30, let me know if that works for you or not. If not, I am sure I can come up with alternative solution that will.