Create related data in a related data: lead to 422 status code

Thank you for your patience.

I just found a different thread for one of the issues you faced with the same model.

Unfortunately, the issue is still the same - we do not support well the composite primary key. I am sorry about this limitation

I reported the issue to our technical team and you can follow the progress here.

I am really sorry to not be able to be of any help to you. If I can do something more to help you please let me know.