const
  JsonToDeserialize =
    '[{"customerNumber":"string","type":"string","name":"string","entityDetails":{"organizationType":"string","numberOfOwners":0,"dateOfFoundation":"2019-11-06T17:10:00"},'
    + '"naturalDetails":{"lastName":"string","firstName":"string","middleName":"string","dateOfBirth":"2000-01-01","gender":"string","maritalStatus":"string","numberOfFamilyMembers":0},'
    + '"idDocument":"string","address":"string","addressArea":[{"value":"string"}]}]';

function RefCount(const _s: AnsiString): Integer;
var
  ptr: PLongWord;
begin
  ptr := Pointer(_s);
  Dec(ptr, 2);
  Result := ptr^;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  MyRec: TDatas;
  LJson: RawUTF8;
begin

  LJson := JsonToDeserialize;
  ShowMessage(InttoStr(RefCount(AnsiString(LJson))));
  UniqueRawUTF8(LJson);
  ShowMessage(InttoStr(RefCount(AnsiString(LJson))));
  // This will now work because we have a unique string
  if SynCommons.DynArrayLoadJSON(MyRec, Pointer(LJson), TypeInfo(TDatas)) = nil then
    ShowMessage('Json de-serialization failed')
  else
    ShowMessage('Json successfully transfered in record');