A short list for the week before gates open, written for whoever is responsible when a counter goes quiet.
Run a real order through every station, start to finish, with a real payment and a real ticket. Not a test mode: the thing that breaks is usually between systems, and a test that stops short of the counter does not test the part that fails.
Then unplug one station and watch what the venue does. Whoever is on shift should know within a minute, and should know who to tell. If finding out depends on a guest complaining, that is the gap to close before the gates open.
One person watches the stations, not the queue. Queues are visible and self-reporting; a counter that has stopped printing looks exactly like a counter with no orders, and the two are impossible to tell apart from across a field.
Count tickets against sales per station, the same evening if you can. The gap between those two numbers is the only honest measure of whether the hand-off worked, and it is a conversation worth having while everyone still remembers the night.