Filter multiple dynamic dropdown lists within one form using the Smart Grid-layout extension for Contact Form 7

Try this instead, combine all 3 functions into a single one,

add_filter('cf7sg_dynamic_dropdown_custom_options', 'filter_options',10,3);
function filter_options($options, $field_name, $form_key){
  //field 'dynamic_select-461'
  if($form_key == 'bez-nazvu' && $field_name == 'dynamic_select-461') {
    $options = array(); 
    //get your terms
    $terms = get_the_terms( $post->ID , 'strava' );
    if( ! empty( $terms ) && ! is_wp_error( $term_args ) ) {

      foreach( $terms as $term ) {
        //this is the <option value="">label</opton> value->label pairs.
        $options[$term->name] = $term->name;
      }
    }
  }
  //field 'dynamic_select-462'
  if($form_key == 'bez-nazvu' && $field_name == 'dynamic_select-462') {
   $options = array(); 
   //get your terms
   $terms = get_the_terms( $post->ID , 'doprava' );
   if( ! empty( $terms ) && ! is_wp_error( $term_args ) ) {

     foreach( $terms as $term ) {
       //this is the <option value="">label</opton> value->label pairs.
       $options[$term->name] = $term->name;
     }
   }  
  } 
 //field 'dynamic_select-463'
 if($form_key == 'bez-nazvu' && $field_name == 'dynamic_select-463') {
   $options = array(); 
   //get your terms
   $terms = get_the_terms( $post->ID , 'terminy' );
   if( ! empty( $terms ) && ! is_wp_error( $term_args ) ) {
     foreach( $terms as $term ) {
       //this is the <option value="">label</opton> value->label pairs.
       $options[$term->name] = $term->name;
     }
   }  
   
  }
  return $options;
}