How to Manage Webhook Notifications?

I had developed a controller to retrieve data from an API via a webhook. This is the type of data I received with https://webhook.site for testing :

{
  "owner": {
    "id": "100000",
    "userName": "lorem"
  },
  "notes": "",
  "created": {
    "dateTime": "2021-12-14T18:54:36",
    "timeZone": "Europe/Paris"
  },

Here is a preview of the controller :

    class WebhookLoremController extends ControllerBase {

        public function LoremListener(Request $request) {

            $data_webhook = $request->getContent();
     
            // data is invalid       
            dump($request);
            
            // data is invalid    
            dump($data_webhook);

            // obviously doesn't work as $data_webhook is invalid
            $decode = Json::decode($data_webhook);

         }

    }

Everything was working fine but now the data received is invalid. We can see the @ character for example, or problems with comma, colon, or } :

{
   "owner":"@""id":"100000",
   "userName":"lorem",
   "notes":"",
   "created":"@""dateTime":"2021-12-14T18:54:36",
   "timeZone":"Europe/Paris",

I immediately thought of a problem with the API but I have no problem if I test with https://webhook.site. I take it that the problem is on my side. If I dump $request the problem is already there.

It worked before and I did not change the code. The only thing I'm thinking about is that I updated to Drupal 9 but I'm not sure if that has anything to do with it.

Do I have to do something with drupal to retrieve this kind of data?

EDIT

Here is the dump() of $request :

"POST /webhook/listener-api-lorem-10000 HTTP/1.1 Authorization":"Content-Length":"3607 Content-Type":"application/json Host":"lorem.fr User-Agent":"Jakarta Commons-HttpClient/3.1 X-Agendize-Objectevent":"deleted X-Autonomous-System":"16276 X-Country-Code":"FR X-Forwarded-Port":"443 X-Forwarded-Proto":"https X-Php-Ob-Level":"1 X-Ssl":"yes"{
   "owner":"@""id":"10000",
   "userName":"lorem",
   "notes":"",
   "created":"@""dateTime":"2021-12-14T20:04:36",
   "timeZone":"Europe/Paris"