cn-s=Search. The shim script is causing the placeholder text “Search” to be sent as if you were filtering by category and search for the word “Search” and it shouldn’t be. Obviously, this is not what you want to do.
Unfortunately, other than changing themes, which I would never ask someone to do, the only solution is to make a small edit to Connections so it does no longer use the placeholder text.
class.template-parts.php file found here:
Search for this line, should be on line 466:
$out .= '<input type="text" id="cn-search-input" name="cn-s" value="' . esc_attr( $searchValue ) . '" placeholder="' . __('Search', 'connections') . '"/>';
Replace it with this:
$out .= '<input type="text" id="cn-search-input" name="cn-s" value="' . esc_attr( $searchValue ) . '"/>';
Save and upload overwriting the original. Of course you should make a backup first.
Now, because the placeholder text is no longer in place, the shim script from the theme will no longer affect the category filter.
Hope that helps.