CNContactStore executeSaveRequest error with (CNErrorDomain 2 error.)

Question

I am trying to remove URL redundancy in my application. This works well if a single contact has multiple URLs. But if there are connected contacts, as a rule, a failure to work with the message "Operation could not be completed (CNErrorDomain error 2.)"

Any tips on getting around this? Does it work with a single contact? If the removal of the URL should occur separately for individual non-unified elements, is there a way to get them from a single one?

Here is an excerpt from the code:

CNSaveRequest *saveRequest = [[CNSaveRequest alloc] init];

NSArray* keys = @[CNContactUrlAddressesKey];
NSPredicate *predicate = [CNContact predicateForContactsWithIdentifiers:identifiers];
NSError *error;
NSArray <CNContact *> *contacts = [_contactStore unifiedContactsMatchingPredicate:predicate keysToFetch:keys error:&error];

for (CNContact *contact in contacts) {
 // here we'll collect non-ambigous URLs
  NSMutableArray<CNLabeledValue<NSString *> *> *copyOfURLs = [NSMutableArray array];
 // just a marker for the moment if a URL with specific prefix was already found
  NSString *baseURL = nil;
  for (CNLabeledValue<NSString *> *labeledValue in contact.urlAddresses) {
    NSString *url = labeledValue.value;
    if ([url hasPrefix:APP_IDENTITY_URL_SCHEME]) {
       if (baseURL == nil)
         baseURL = url;
       else
         continue;
     }
     [copyOfURLs addObject:labeledValue];
  }
  CNMutableContact *updatedContact = [contact mutableCopy];
  updatedContact.urlAddresses = copyOfURLs;
  [saveRequest updateContact:updatedContact];
}
NSError *saveError;
if (![_contactStore executeSaveRequest:saveRequest error:&saveError]) {
  NSLog(@"Saving error: %@", saveError.localizedDescription);
}