iOS Location Reminder App misses certain location - ios

Question

We are building location based reminder app and it works in 7 case out of 10. It simply misses certain locations. Can you please suggest what would be the possible issue with that?
Following is the logic we are using for location matching.
-(void)locationChangeLogic {
CLLocation *currentLocation = [[CLLocation alloc] initWithLatitude:latitudeTemp longitude:longitudeTemp];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// Perform long running process
NSArray *arrayLocations = [[NSArray alloc] initWithArray:[[self db] getListOfLocations]];
NSMutableArray *arrayToNotification = [[NSMutableArray alloc] init];
if ([arrayLocations count] > 0) {
for (NSDictionary *dict in arrayLocations) {
CLLocation *newLocation = [[CLLocation alloc] initWithLatitude:[[dict valueForKey:#"latitude"] floatValue] longitude:[[dict valueForKey:#"longitude"] floatValue]];
float miles = [[NSUserDefaults standardUserDefaults] floatForKey:#"miles"];
CLLocationDistance distance = [currentLocation distanceFromLocation:newLocation];
//Set matched objects and update flag
if ((distance/1609.344) <= miles) {
if ([[dict valueForKey:#"isSelected"] integerValue] == 1) {
[arrayToNotification addObject:dict];
}
//Matched location FLAG will going to 0, so notification not get fire twice or repeatedly
}else {
//The location which are not in current redius, we will make those location FLAG to 1, So when user enter in different location it will check for that
}
}
}
dispatch_async(dispatch_get_main_queue(), ^{
if ([arrayToNotification count] > 0) {
[self setAndFireLocalNotifications:arrayToNotification];
}
});
});
}
Any help would be appreciated.