I am not sure why this is showing for you. If otherwise it is working, you need to follow the advice from the PHP manual and make sure that the PHP variable display_errors is set to OFF (in php.ini).

From what you write, it is ON and that is not correct/normal server PHP setup.

For PHP 5.x by default this setting is ON on first install, for PHP 7 they have fixed it and it is OFF by default.

I went to the page that I could see in the video and the works for me, even after a selection is made. I do see that the form uses Ajax and that the Ajax Container is set to #main and instead it should be either .posts or #destinations (as they are the containers that hold the results. I am not which it should be.

It looks like your search form results page is using your standard archives.php template file. Thus it is your theme that is doing this.

The following suggestion assumes that you are using a child theme, and not a master theme (Orbisius do a free child theme maker plugin to make this easy if you are not using a child theme):

It may be possible to copy this template file into the child theme folder and rename it (e.g. search-results.php) and set the form to use that. If the page still has the wrong title, you may need to edit the template file. You might be able to hard code the title.