AFNetworking，使用共享AFHttpSessionManager，待处理请求在更新请求完成时被取消

Question

我在单例模式下使用AFHTTPSessionManager，并启动多个请求，如：

[MyAPI testSlow]; 
[MyAPI testQuick];

MyAPI定义：

+(void)testSlow { 
AFHTTPSessionManager *manager = [BPNetworkManager sharedManager]; // Get Manager Singleton 
NSString *urlString = [BPCommonUtils getUrlByPath:@"/api/test/testSlow"];
[manager GET:urlString parameters:nil success: ^(NSURLSessionTask *operation, id responseObject) { 
   NSLog(@"slowSuccess"); 
} failure:^(NSURLSessionTask *operation, NSError *error){ 
   NSLog(@"slowFail"); 
}];

}

+(void)testQuick { 
AFHTTPSessionManager *manager = [BPNetworkManager sharedManager]; 
NSString *urlString = [BPCommonUtils getUrlByPath:@"/api/test/testQuick"]; 
[manager GET:urlString parameters:nil success: ^(NSURLSessionTask *operation, id responseObject) { 
NSLog(@"quickSuccess"); 
} failure:^(NSURLSessionTask *operation, NSError *error){ 
NSLog(@"quickFail"); 
}]; 
}

当“快速任务”成功返回时，“慢速任务”立即失败，消息信息失败： @“NSURLErrorDomain” - 代码：18446744073709550617

@“NSLocalizedDescription”：@“已取消”

我该如何解决？谢谢！