At a quick glance it seems as though $double_encode should be set to false in the a couple of spots in the acf core when using htmlspecialchars:
http://php.net/manual/en/function.htmlspecialchars-decode.php
For now i just wrote a simple decode function that I run after get_field and before update_field:
public function htmlspecialchars_decode_array($array){
$newArray = array();
foreach($array as $arrayKey => $arrayVal){
$newArray[$arrayKey] = htmlspecialchars_decode($arrayVal);
}
return $newArray;
}
