Elasticsearch nested query for registration fails when second registration added

[bhalsey]

Elasticsearch nested query for registration fails when second registration added

Description

It has been observed that a nested query for users registered to an application is not returning complete results.

The query is essentially of the form (but also using pagination and sorted fields):

"search": {
    "query": "{\"nested\":{\"path\":\"registrations\",\"query\":{\"bool\":{\"must\":[{\"match\":{\"registrations.applicationId\":\"{{applicationId1}}\"}}]}}}}"
  }
}

A user that is known to be registered to application1 is not returned in the results. This user is registered to a second application, and they are returned when the above query uses applicationId2.

A clear and concise description of what the bug is.

Observed versions

1.55.1

Steps to reproduce

It is unclear how to reproduce this. Possibly a race condition.

Expected behavior

The user should be returned in nested queries for either application.