When clone a field or a group, the values of that field or sub-fields will be cleared. This is the expected behavior so users can enter new values in the new cloned fields.
In case you want to keep a pre-defined value for a field/sub-field, please set
'clone_default' => true for the field/sub-field (in this case, probably is the radio field). This parameter will auto set the
std value for new cloned field.