Can't start or stop streaming session with Nimble Studio API

I'm trying to automate the start and stop of a streaming session using AWS Nimble Studio API.

I'm using Python Boto3 API, and although I got the expected result using other Nimble API methods, start_streaming_session() and stop_streaming_session() respond with "Unknown error parsing request body".

At this point, I have no idea what I am doing wrong.

I've tried to use AWS CLI, and the outcome is the same.

I used my account admin IAM user credentials with the Admin Access policy attached.

Here are the logs. I've replaced sensitive information with placeholders. nimble_studio_logs.txt

And here is the script I'm using :

boto3.set_stream_logger('')
session = boto3.Session(aws_access_key_id='my-admin-key', aws_secret_access_key='my-admin-secret-key')
nimble_client = session.client('nimble', region_name = 'eu-west-2')
studio_id = nimble_client.list_studios()['studios'][0]['studioId']
sessions = nimble_client.list_streaming_sessions(studioId=studio_id)['sessions']

for session in sessions:
    if session['state'] == "STOPPED" and \
        session['tags']['aws:nimble:createdWithLaunchProfile'] == 'my-launch-profile-id':
            the_session = session

if the_session:
    response = nimble_client.get_streaming_session(sessionId=the_session['sessionId'],studioId=studio_id)
    response = nimble_client.start_streaming_session(sessionId=the_session['sessionId'],studioId=studio_id)```