Nested aka Sub-document entities with ID property not generating ID (ObjectId) on create

Steps to reproduce

1. Create an entity with an ID (ObjectId) property.
2. Create another entity with an ID (ObjectId) property.
3. Add a nested/sub-document property to the first entity referencing the second entity as the type; alternatively create an array of nested/sub-documents to the first entity referencing the second entity as the type.
4. Create a new instance of the first entity and create and add an instance of the second entity to the first.
5. Call save/create to persist to the database.

Current Behavior

1. First entity will have an ObjectId automatically generated as is confirmed by inspection the record in the database.
2. The child/nested/sub-document(s) (second entity) will have no ObjectId present in its ID property.

Expected Behavior

1. First entity will have an ObjectId automatically generated as is confirmed by inspection the record in the database.
2. The child/nested/sub-document(s) (second entity) would have an ObjectId present in its ID property that was automatically generated and should be the same for any further nested/sub-documents.

Additional information

Tested w/ 6.0.1.

I've used LB4 in several production applications so far and am a big proponent. That being said, this issue is severely hampering usage of MongoDB in real-world use cases where nested/sub-documents and nested/sub-document arrays are ever-present. Requiring workarounds by using juggler lifecycle events. Any attempt to resolve it is greatly appreciated. I also distinctly remember this working at one point and am not sure if this is a regression.

Start by reproducing the issue with a MongoDB entity containing a nested entity or nested-entity array, following the listed steps. Compare the parent and child ID properties after save/create; done means newly created nested entities consistently receive an ObjectId matching the expected persisted behavior.