Video shows the how to do the easter egg on mill when the 40 second keypad method doesn't work. I'm not sure if this is the newer or older version of the map.
Do note: The keypad in the end can only be used once. If you use it before completing all the triggers, it will not work again until the next round.
The fifth trigger in the video can be boosted on and is probably recommended to do so to have a guarantee activation of the trigger. In my testing, my method has been consistent if you jump towards the middle of the roof/ceiling thing.