title: Irregular GATT_INVALID_HANDLE error on python GATT server
body: <p>I am facing a problem with my flutter app accessing a GATT python endpoint. Sometimes, I do receive the following error message reading a characteristic on my remote machine (RPI 3b):<br />
  <code>Unhandled Exception: Exception: GenericFailure&lt;CharacteristicValueUpdateError&gt;(code: CharacteristicValueUpdateError.unknown, message: &quot;GATT exception from MAC='XX:XX:XX:XX:XX:XX', status 1 (GATT_INVALID_HANDLE), type BleGattOperation{description='CHARACTERISTIC_READ'}. (Look up status 0x01 here https://android.googlesource.com/platform/external/bluetooth/bluedroid/+/android-5.1.0_r1/stack/include/gatt_api.h)&quot;)</code></p>
  <p>I had a look at the link, but there is just the actual name of the error which is GATT_INVALID_HANDLE. The docs are not quite helpful...<br />
  For some reason it does work sometimes after restarting both the GATT server and the app several times.</p>
  <p>Does anyone faced such an issue with BLE?</p>
  <p>Best and thanks in advance</p>