The issue happens because updating the Crew Leader (CL) on the Route detail screen does not automatically update the CL on work tickets that are already scheduled as visits.

When work tickets are generated after winning an opportunity, and subsequently scheduled , the CL assigned to that specific scheduled ticket (Visit) is saved. If the CL changes on the route, you must update the CL on each scheduled work ticket manually.

The problem is compounded if the employee is inactive, as deactivated employee records are generally removed from new search lists but cannot be deleted for historical purposes. Best practice when offboarding a CL is ensuring all their existing scheduled work tickets are reassigned to an active CL before the former employee's user or contact record is deactivated

Only way to clean this up would be by editing / redoing the existing recurring schedule.