Select Field Not Updating

I have the same problem.

I checked the $_POST in acf_location_nav_menu_save_post() in fields_actions.php and it only prints one value so maby WP is removing them from $_POST before your function is called?

I Think i found some thing.

This is what is posted to WP:

  {  
      "name":"acf[35][field_58be7320d7192][]",
      "value":"theme_teaser_color_gray"
   },
   {  
      "name":"acf[35][field_58be7320d7192][]",
      "value":"theme_teaser_color_beige"
   },
   {  
      "name":"acf[35][field_58be7320d7192][]",
      "value":"theme_teaser_color_green"
   },

When I’m dumping $_POST[‘acf’] in fields_actions.php – acf_location_nav_menu_save_post()

array (size=14)
  35 => 
    array (size=3)
      'field_58be720bba9d7' => string 'theme_teaser' (length=12)
      'field_58be72f4d7191' => string '12' (length=2)
      'field_58be7320d7192' => 
        array (size=1)
          '' => string 'theme_teaser_color_green' (length=24)

When dumping $_REQUEST[‘acf’] in fields_actions.php – acf_location_nav_menu_save_post():

array (size=14)
  35 => 
    array (size=3)
      'field_58be720bba9d7' => string 'theme_teaser' (length=12)
      'field_58be72f4d7191' => string '12' (length=2)
      'field_58be7320d7192' => 
        array (size=5)
          0 => string 'theme_teaser_color_red' (length=22)
          1 => string 'theme_teaser_color_white' (length=24)
          2 => string 'theme_teaser_color_gray' (length=23)
          3 => string 'theme_teaser_color_gray_dark' (length=28)
          4 => string 'theme_teaser_color_black' (length=24)

———–

It works if i change line 37 from
if( empty($_POST['acf']) )
to
if( empty($_REQUEST['acf']) )

And changing line 45 from:
foreach( $_POST['acf'] as $item_id => $item_fields )
to
foreach( $_REQUEST['acf'] as $item_id => $item_fields )

Also having the same issue. Does this solution 100% work?

Thanks in advance!