POST Error 500: must implement interface EntityInterface, null given

I'm having an Error 500 on POST requests, something related about an EntityInterface.

The error on the server is.

TypeError: Argument 1 passed to Drupal\Core\Entity\EntityRepository::getTranslationFromContext() must implement interface Drupal\Core\Entity\EntityInterface, null given, called in /www/conventus/docroot/web/modules/contrib/jsonapi/src/Normalizer/EntityReferenceFieldNormalizer.php on line 92 in Drupal\Core\Entity\EntityRepository->getTranslationFromContext() (line 82 of /www/conventus/docroot/web/core/lib/Drupal/Core/Entity/EntityRepository.php)

The request is a POST to /jsonapi/node/article?_format=api_json

The body:

{
  "data": {
    "type": "node--article",
    "id": "d9ad5222-c502-46fb-ace4-7d510cb9960a",
    "attributes": {
      "uuid": "d9ad5222-c502-46fb-ace4-7d510cb9960a",
      "langcode": "sv",
      "title": "Asdasd asdasd asdad",
      "status": 0,
      "created": 1485872587,
      "changed": 1485872626,
      "promote": 0,
      "sticky": 0,
      "revision_timestamp": 1485872626,
      "revision_log": null,
      "revision_translation_affected": null,
      "default_langcode": true,
      "path": {
        "alias": "",
        "pid": null
      },
      "body": {
        "value": "<p>ASdasd asdasdas asdasd asdasdas dasdasd asdasda sda sdas&nbsp;</p>\r\n",
        "format": "editor_mode",
        "summary": ""
      },
      "field_extra_title": "ASdasd",
      "field_feature_place": "9",
      "field_ingress": {
        "value": "<p>Asdasdads asdasd asdasdasd asdasdasd</p>\r\n",
        "format": "editor_mode"
      },
      "field_teaser": "ASdasd",
      "field_tt_job": null,
      "own_publish": 1
    },
    "relationships": {
      "uid": {
        "data": [
          {
            "type": "user--user",
            "id": "62d1f7fd-b871-4c6c-9873-58995d70f76e"
          }
        ]
      },
      "revision_uid": {
        "data": [
          {
            "type": "user--user",
            "id": "62d1f7fd-b871-4c6c-9873-58995d70f76e"
          }
        ]
      }
    }
  }
}

I'm trying to debug to find where is my error. If someone have some advice about it, please shoot.