Custom meta box values are not getting saved for my custom post type

but remaining values (checkbox, select, images) are not getting saved

I believe those fields are also getting saved, but you are just not displaying them correctly. And you should always escape input/textarea values, e.g. use esc_attr() for single-line inputs and esc_textarea() for textareas (multi-line inputs).

So to make your code work correctly, try these:

• First off, you can define default values for your your_fields meta like so, which uses wp_parse_args():

  $meta = get_post_meta($post->ID, 'your_fields', true);
  
  // Merge with default values, ensuring all keys are set.
  $meta = wp_parse_args( $meta, array(
      'text'     => '',
      'textarea' => '',
      'checkbox' => '',
      'select'   => '',
      'image'    => '',
  ) );
  

• Then use the following to display your form fields: (just replace the corresponding field in your existing code)

  <input type="text" name="your_fields[text]" id="your_fields[text]" class="regular-text"
      value="<?php echo esc_attr( $meta['text'] ); ?>">
  
  <textarea name="your_fields[textarea]" id="your_fields[textarea]" rows="5" cols="30"
      style="width:500px;"><?php echo esc_textarea( $meta['textarea'] ); ?></textarea>
  
  <input type="checkbox" name="your_fields[checkbox]" value="checkbox"
      <?php checked( $meta['checkbox'], 'checkbox' ); ?>>
  
  <select name="your_fields[select]" id="your_fields[select]">
      <option value="">Select..</option>
      <option value="option-one"<?php selected( $meta['select'], 'option-one' ); ?>>Option One</option>
      <option value="option-two"<?php selected( $meta['select'], 'option-two' ); ?>>Option Two</option>
  </select>
  
  <input type="text" name="your_fields[image]" id="your_fields[image]"
      class="meta-image regular-text" value="<?php echo esc_attr( $meta['image'] ); ?>">