Ember: Must include an 'id' in an object passed to 'push'

Currently experiencing the following error: You must include an 'id' for failed-shotlist in an object passed to 'push'. This is in a code base I have inherited mid-development and I am fairly new to Ember.

From what I understand, this occurs when the backend does not respond with an ID. The server payload looks like the following (returning an alert object with an embedded failedShotlist record):

alertAuthor: "Test name"
alertDate:"2018-06-28T16:25:21+12:00"
alertIdentifier:"456e15c7-7a8b-11e8-84a8-06f4aef780e3"
alertType:"failedShotlist"
email:"test@gmail.com"
failedShotlist:{projectName: "8888 st", shotlistIdentifier: "79d52773-5faf-11e8-84a8-06f4aef780e3",…}
    projectIdentifier:"79050dfb-5faf-11e8-84a8-06f4aef780e3"
    projectName:"8888 st"
    projectRoleENUM:"bp"
    projectRoleName:"Building Participant"
    shotlistDescription:"Framing"
    shotlistIdentifier:"79d52773-5faf-11e8-84a8-06f4aef780e3"
inviteIdentifier:null
profileId:"c4e02bee-3d26-11e8-84a8-06f4aef780e3"
shotlistIdentifier:"79d52773-5faf-11e8-84a8-06f4aef780e3"

Since the backend doesn't respond with an ID attr, the primary key needs to be transformed using a serializer's 'primaryKey' property:

serializers/alert.js

export default ApplicationSerializer.extend(EmbeddedRecordsMixin, {
  primaryKey: 'alertIdentifier',

  attrs: {
    'invite': { deserialize: 'records' },
    'failedShotlist': { deserialize: 'records' },
  },
});

I couldn't find any mention of this, but I assume that embedded records are further serialized by their own serializers. The existing one is as follows:

serializers/failedShotlist.js

export default ApplicationSerializer.extend({
  attrs: {
    'shotlistId': { key: 'shotlistIdentifier' },
    'projectId': { key: 'projectIdentifier' },
  },
});

Since the ID's for the failedShotlist object also need to be transformed, I have updated this to include the primaryKey prop:

serializers/failedShotlist.js

export default ApplicationSerializer.extend({
  primaryKey: 'shotlistIdentifier',

  attrs: {
    'shotlistId': { key: 'shotlistIdentifier' },
    'projectId': { key: 'projectIdentifier' },
  },
});

Unfortunately, this results in the same error I originally encountered. Any ideas as to how this might be resolved?