Maybe you have blocked with that Staff position , importent points , for example the points where the pax need to go the baggage scanner. Then you get problems. It is like you build a cabinet infront of a vending machine , then the pax also can not use the vending maschine.

I just tested the mod(also the security positions) both work. so it must be a local problem at your airport. Maybe because of a script mod(from QCS or Flash) To find your problem you need to come to SA Discord (link is in the SA Discussions) there you can send us your save, then we can test it.

The doubleticket desks also work without the second staff (that is just, that it looks better)

This mod now creates a lot of problems, so I had to unsuscribe, and I won't be able to use the double ticket desk. Shame, because it was such a great ideas!