Laravel validation odd behavior

I'm working on a file upload and it upload well until I try to get a file I'm not supposed to be able to upload.

My rules are:

 public function rules()
    {
        return [
            'media' => ['required', 'image', 'max:2000']
        ];
    }

public function messages()
    {
        return [
            'media.required' => 'You must give a file to upload!',
            'media.image'    => 'The file is not an image!',
            'media.max'      => 'The file is too big!',
        ];
    }

and when I try to upload a file which is 2,3Mo I got a 422 but the message is always The given data is invalid without telling me which one is invalid.

Then in my controller, this is how I use it:

public function uploadMedia(AddMediaRequest $request, MyEntity $entity)
    {
        $filename = $entity->addMedia($request->validated());

        return response()->json(['filename' => $filename], 200);
    }

Am I missing a simple point ? (I use Vue for the front end with axios)