Changing assignee is not automatically reflected on a Kanban board

Issue Summary

On a Kanban board configured with Assignee swimlanes data is not always automatically refreshed after the Assignee changes.  

Steps to Reproduce

1. Open a Kanban Board with Assignee swimlanes configured
2. In a second tab change the Assignee in one of the issues displayed on the board
3. Observe the changes on the board; automatic refresh may take from 1 to 60 seconds to update the Assignee. 

Expected Results

The board should be refreshed instantly reflecting changes in the Assignee

Actual Results

Occasionally it takes up to 1 minute for the changes to be reflected on board.

Workaround

Manual reload of the page.