To completely disable this feature, use this code, which I got from here.
remove_action( 'template_redirect', 'redirect_canonical' );
To only disable it for URL addresses that contain the string ‘event’, use this code:
add_filter( 'redirect_canonical', 'disable_redirect_canonical_for_event', 2, 10 );
function disable_redirect_canonical_for_event( $redirect_url, $requested_url ) {
if ( strpos( $requested_url, 'event' ) !== false ) {
return false;
}
return $redirect_url;
}