Nested object and arrays not saved correctly on database

Using spring-data-couchbase 4.0.0 reactive implementation
Examples in the documentation, say an object should be saved like this:

{
  "_class": "foo.User",
  "children": [
    {
      "age": 4,
      "name": "Alice"
    },
    {
      "age": 3,
      "name": "Bob"
    }
  ],
  "firstnames": [
    "Foo",
    "Bar",
    "Baz"
  ],
  "inner": {
     "name": "foo"
 }    
}

It worked like that in the previous version, but now it is saved like this:

{
  "_class": "foo.User",
  "children":{
"empty": false
},
  "firstnames": {
     "empty": false
 },
 "inner": {
    "content": {
        "name": "foo"
    },
    "id": null,
    "expiration": 0
 }
}

My inner @Document class does not even have an id field or an expiration.

Found the ticket https://jira.spring.io/projects/DATACOUCH/issues/DATACOUCH-560?filter=allopenissues