This issue has been resolved.
For tasks to which a job role and specific users within the job role are assigned, when you use inline editing to unassign a user, the user's job role is also unassigned. The expected behavior is for the user to be unassigned and job role to remain assigned to the task.
The development team is working to resolve this issue.
For a workaround, you can unassign the user from the task in the Task details box.