BLE.begin() succeeds only the first time in Arduino giga

Running this code in Arduino giga:

```
void loop()
{
  if(BLE.begin())
    Serial.println("OK");
  else
    Serial.println("KO");

  BLE.end();
}
```

show OK only the first time. For all subsequent calls it always show KO and this make impossible to use bluetooth again after the first end().