Hi,
Thank you for the details!
It seem that the search override feature caused the conflict, I have turned it off. It is not required in this case because the custom URL is not actually the search results page, and that somehow affected the query string not to include the correct search argument.
From the back-end it works now, you will have to clear all layers of cache and refresh the home page – I was not able to do it, even after clearing all cache still the outdated page was pulled. Once cleared, it will be resolved.