iBeacon: didDetermineState never called when exiting a region

I'm trying to monitoring region and detecting beacons when the app is killed (in foreground everything works fine). I've read that it should be sufficient to set allowsBackgroundLocationUpdates=true and pausesLocationUpdatesAutomatically=false to wake up the app, but only if an enter/exit event is detected.

Now, my problem is that when I turn off the beacon, didDetermineState and didExitRegion are never called. And if I request the state explicitly, it return that it is still inside the region. What am I missing?

This is my code, entirely in the AppDelegate.

func requestLocationPermissions() {
        locationManager = CLLocationManager()
        locationManager.delegate = self
        locationManager.requestAlwaysAuthorization()
        locationManager.allowsBackgroundLocationUpdates = true
        locationManager.pausesLocationUpdatesAutomatically = false
        
        startMonitoring()
}

func startMonitoring() {
        let constraint = CLBeaconIdentityConstraint(uuid: Config.Beacons.uuid, major: Config.Beacons.major, minor: Config.Beacons.minor)
        let beaconRegion = CLBeaconRegion(beaconIdentityConstraint: constraint, identifier: Config.Beacons.beaconID)
        beaconRegion.notifyEntryStateOnDisplay = true

        locationManager.startMonitoring(for: beaconRegion)        
        locationManager.startRangingBeacons(satisfying: constraint)
}

func locationManager(_ manager: CLLocationManager, didDetermineState state: CLRegionState, for region: CLRegion) {
        if state == .inside {
            print("AppDelegate: inside beacon region")
        } else {
            print("AppDelegate: outside beacon region")
        }
}
    
func locationManager(_ manager: CLLocationManager, didEnterRegion region: CLRegion) {
        print("AppDelegate: entered region")
}
    
func locationManager(_ manager: CLLocationManager, didExitRegion region: CLRegion) {
        print("AppDelegate: exited region")
}
    
func locationManager(_ manager: CLLocationManager, didRange beacons: [CLBeacon], satisfying beaconConstraint: CLBeaconIdentityConstraint) {
        guard beacons.count > 0 else {
            let constraint = CLBeaconIdentityConstraint(uuid: Config.Beacons.uuid, major: Config.Beacons.major, minor: Config.Beacons.minor)
            locationManager.requestState(for: CLBeaconRegion(beaconIdentityConstraint: constraint, identifier: Config.Beacons.beaconID))
            return
        }
        
        // Other stuff
 }