Summary

Issue span in multiple column when parent issue in backlog and subtask in other status.
Seems to also happen when an issue is appearing in the Kanban board just below a normal sub-task and there's no cards in the other columns.

Environment

• Version 7.2.0-OD-03-012

Steps to Reproduce

1. Enable Kanban Backlog (lab) feature.
2. Create issue + subtask.
3. Move the sub-task issue to any other column, while keeping the parent in the Backlog column.

Expected Results

Issues should not span multiple columns.

Actual Results

Issues span multiple column.

Workaround

Either one of the following can be used to workaround the problem:

1. Move the parent issue type out of the backlog, OR
2. Disable Kanban Backlog (lab) feature, OR
3. Create a quick filter status != Backlog
4. Quick filter status not in (status1, status2, ...) if you have multiple statuses in the backlog

Notes

Oftentimes, disabling the Kanban Backlog Labs feature may turn the first board status as "Unmapped", removing some issues form the board.

If the Swimlanes setting in the board configuration is set to "Stories", the board will display entirely blank instead and you get an error in the Javascript console: TypeError: undefined is not an object (evaluating 'm.key') (line 175 from includes/js/rapid/ui/work/GridSwimlanesData.js).