Ibeacon sometimes can't notify me '- (void)locationManager:(CLLocationManager *)manager didExitRegion:(CLRegion *)region'

[huzhongyin]

Hello：
When I test my app，I found that '- (void)locationManager:(CLLocationManager *)manager didExitRegion: (CLRegion *)region', this method was not executed sometimes,nearly ten percent .Do you know why is it ?
Thank you very much!!!