For whatever reason, the app gets unloaded by the OS very quickly after losing focus, for example, when briefly switching to the Camera app to snap a photo. This wouldn't be a problem if the app saved your place in the tour, but the best it offers you with the location services it requests is a map of all the checkpoints with your current location marked, which takes three taps to reach from the home screen. This is a tedious & repetitive process that detracts from the intended tour experience.
This problem is at least countered by some smart design choices, like being able to easily preload all the video content in advance, which barely took a minute over the lobby WiFi.