HTTP error response payload not delivered

Thanks a lot for your comment.

I have no direct access to the F5 unfortunately, but as far as i can test on a working environnement, the backend server seems to simply not crafting any JSON at all.

On the client page, a small window is expected JSON data, but it is having instead a 422 HTTP message, that to my understanding, could not contain any response data.

The application team was suspecting the F5 device to remove or replace any data that was being responded to the client. I have checked already that no stream or any other manipulation action was in place. I should have more details soon.