PUT user field returns 204 but doesn't update

[Leticia]

Jira Software version: v7.10.1

When making a user field update (PUT) using REST, the response is successful but the field isn't actually updated. Same happens with POST when creating a new task and trying to set the custom user field. I've tried:

1. Assigning user with /assignee
2. Updating a custom user field (+ setting this field when creating task)

The API call I made, with basic auth, from postman:

• Custom user field:

{ "fields":
  { "customfield_10901": 
    { "emailAddress": "xyz@xyz.com" }
  }
}

• Assignee:

{ "emailAddress": "xyz@xyz.com" }

The response:

• 204 No Content
• X-AUSERNAME header returns the correct user to the email informed.

But the field stays empty as you can see below:

Is there anything that could solve this?

[tung.tran]

I got the same issue and want to checkin if you have solution yet @Leticia ?