Column Formatting of the Kanban board is gone in Subtask's Assignee view

Issue Summary

The columns of the Kanban board is messed up (subtask assignee view) and the assignee is not able to drag&drop the issues to the correct column within the board.

Keywords: Kanban cards spanning, stretching, distorting through multiple columns statuses.

Environment

JIRA 8.1.0

Steps to Reproduce

1. There are two users involved
   • User 1 - the admin user who executes the operation and is a member of Group1 security level.
   • User 2 - not a member of Group 1 security level, current assignee of the subtask
2. There's one security level called Group 1 which is the default security level when the issues are created.
3. The User 1 (admin) created a task (ABC-1) which automatically has a security level 1 then created a subtask (ABC-2) which the admin user assigned to User 2 (not a member of Group 1 security level)
4. As User 1 (admin), I viewed the Kanban board and the columns are all intact
   
5. I then login as User 2 (assignee of the subtask) but the Kanban board's columns have no more partition and doesn't allow the assignee to drag the issues in the columns without partition
   

Expected Results

The columns have partitions.

Actual Results

Column partitions are not respected in Assignee's view (subtask).

Workaround

Remove the security level on the parent issue and refresh the board (subtask assignee's view).

Note

The issue is not reproducible in JIRA 7.0.10 and 7.13.4. One thing that I noticed is that since the User 2 has no visibility with the parent task (due to security level), he's not able to view it in the board unlike with 8.1.0.