Thing is, the lanes are supposed to be 1+1, and we're supposed to call back up if the lines are longer than that. SETLs are also instructed to stay off the lanes. So they often can't just jump on and take care of those one or two extra guests. What happens is, you get a bunch of lanes with three total parties in them, and yes that's supposed to be a call for backup, by the book. But the time it takes for somebody to stop what they are doing and get to the front, well a lot of the time, the line is short enough by that point, and you don't need the backup. Also, if the third person in a couple of these lines jumps over to SCO, we can't control that. So hopefully, the SETL has time to call off the backup, but often, they are pulled into some little thing or another happening at the lanes.
I know it's annoying, but it happens through no fault of the SETL.