I note that you have not, as yet, cleared this setting:

https://www.screencast.com/t/YfLPR7FG0

That setting box should be empty.

At the moment, until V3 is released in a few months, there isn’t a simple way to have one Custom form for multiple URLs, but it might be possible to use this filter:

https://searchandfilter.com/documentation/action-filter-reference/#modify-urls

Where you could detect the current URL and change the form URL accordingly. It might require some custom coding, but this user post may help:

https://support.searchandfilter.com/forums/topic/form-on-a-single-post/#post-253659