CBOR aws_iot_dla_publish_get_stream_message message rejected by AWS

[arkhipenko]

Hi
I am in the middle of adopting this library for my project, and I hit an issue I cannot explain:
When aws_iot_download_start runs it eventually calls aws_iot_dla_publish_get_stream_message to get stream message
This triggers publishing a CBOR request on this topic:

00:00:00:05.870 V: publishMessage: topic   : $aws/things/840d8ee419b8/streams/mqtt_poc_test_1/get/cbor
Publish OK: $aws/things/840d8ee419b8/strea00ms/mqtt_poc_test_1/get/cbor

the CBOR string is this:
a5 61 63 63 72 64 79 61 66 01 61 6c 19 08 00 61 6f 00 61 62 72 30 78 46 46 46 46 46 46 46 46 46 46 46 46 46 46 37 46
which online converter represents as

{"c": "rdy", "f": 1, "l": 2048, "o": 0, "b": "0xFFFFFFFFFFFFFF7F"}
(https://cbor.me/)

The issue is that AWS responds with this:

00:00:00:06.019 V: subscribeCB: Data
	topic: $aws/things/840d8ee419b8/streams/mqtt_poc_test_1/rejected/cbor
	payload: ¿dcodekInvalidCboraokInvalidCborgmessagetInvalid CBOR messageamtInvalid CBOR messageÿ

and file transfer does not start.

Sending this version:
{"c": "rdy", "f": 1, "l": 2048, "o": 0, "b": h'FFFFFFFFFFFFFF7F'}
does not work either.

What am I missing. The request looks like what is described in the docu:
https://docs.aws.amazon.com/iot/latest/developerguide/mqtt-based-file-delivery-in-devices.html

Please help!