I reproducibly get an error when attempting to move task 149626 from the "Apr-Jun" column, to the "Backlog" column, in https://phabricator.wikimedia.org/project/view/27/
#1062: Duplicate entry 'PHID-PROJ-w2oxxqq7xappt53glrsm-PHID-PCOL-qjdmfzuo6mkde6myazi7-PH' for key 'boardPHID'
I've checked the workboard with "all tasks" showing, and there are no other tasks with that task-number or title in the backlog column.
I have not yet attempted to change the column via the task's own dropdown menus. (So as to enable reproduction of this bug).