iBeacon and iOS 9 - ios

Question

I'm currently working on app that requires iBeacon monitoring.
I wrote the app one year ago, using iOS 8.x SDK.
It was working as it was supposed to, but now, one year from then, the same code doesn't work anymore (I'm testing it with the same beacons!).
Beacon regions detection has become much more unpredictable.
It has a will of its own.
Some beacons get detected, some are just ignored.
I couldn't find anything relevant on OpenRadar.
A few people complained about something similar on Apple Dev Forums, but Apple never came back to them.
Thoughts?
This is how I initialize the location manager.
self.locationManager = [CLLocationManager new];
self.locationManager.delegate = self;
// Worst accuracy is set in order to preserve battery life.
self.locationManager.desiredAccuracy = kCLLocationAccuracyThreeKilometers;
self.locationManager.allowsBackgroundLocationUpdates = YES;
// Required to keep the app living in the background.
// Background mode "Location Updates" is enabled.
[self.locationManager startUpdatingLocation];

Answer 1

I think before you were using geofences or CLCircular regions. Core location doesn't need any of that code to detect iBeacons. Try setting it up like this:
self.locationManager = [CLLocationManager new];
self.locationManager.delegate = self;
[self.locationManager startMonitoringForRegion:beaconRegion]; // Where "beaconRegion" is a CLBeaconRegion with a UUID that matches the beacon you want to detect (major & minor optional)
beaconRegion.notifyEntryStateOnDisplay = YES;
beaconRegion.notifyOnEntry = YES;
beaconRegion.notifyOnExit = YES;
You also need to add NSLocationAlwaysUsageDescription to your info.plist. Once all that is done, you should begin getting enter and exit events for your beacons through these two methods:
- (void)locationManager:(CLLocationManager *)manager didEnterRegion:(CLRegion *)region;
- (void)locationManager:(CLLocationManager *)manager didExitRegion:(CLRegion *)region;