You should not just add a waypoint, that added waypoint would the last one in the waypoint list of that group. You need first to remove any pending waypoint for the crew group. Also consider that a chopper crew might be composed by several groups so you first need to find out, from the surviving members, how many groups should be affected by the evacuation script. Then, for each group, remove all the existing waypoints (waypoints array and deleteWaypoint command in a loop for each member of the array). And now you can add the corresponding waypoints to the EZ. If the EZ is too far away, it is better to split that distance into several waypoints, this way the AI will be able to solve the paths between current position and next destination better.