Just bought this plugin yesterday. I found out that issue today but i think i have solved it.
1) Go to advanced-custom-fields-pro/fields/radio.php and than line 138
2) Change line 138 to:
if( strval($value) === strval($field[‘default_value’]) ) {
Hope to help you guys.
Sorry, thats not the right answer yet. I’m trying to find out yet that causes that bug
