User Story and Defect 'cards' are switching columns on the Team Board, Kanban Board or any number of list views without being updated by a user. The revision history shows that a user made the change but they did not.
An automated job runs periodically to ensure that stories and defects comply with the mapping setup on the Team Board. Changes to the mapping scheme can cause updates to the Schedule State of stories and defects. It can also cause rollup updates to the parent story or parent feature as the child is adjusted to meet the new mapping criteria.
Changes to mapping can be identified by an Admin by reviewing the Revisions of the Project where the issue is occurring. Search for text, "SCHEDULE STATE MAPPING changed" in the revisions to identify what changes were made, when they were made and by whom.