Printing to ZQ520 fails sporadically with error "read failed, socket might closed or timeout, read ret: -1"

Here's my situation:

1. I'm developing in Xamarin Android, with a Nokia 8 running Android 8.1.0 and printing to a Zebra ZQ520 using the Zebra SDK.

2. I'm connecting over a BluetoothConnectionInsecure connection.

3. The first few occasions print works fine.

4. Print then fails with the error "read failed, socket might closed or timeout, read ret: -1" and I can no longer print.

Code example below. Sometimes I send a signature and I also have retry attempts (they haven't worked). !

zebra.png