didReceiveRemoteNotification: fetchCompletionHandl

Our app utilizes didReceiveRemoteNotification: fetchCompletionHandler: methods UIApplicationDelegate to start a download when a content-available push notification is received.

The individual steps the app takes:

[1] Receive a notification

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult result))completionHandler {
    NSLog(@"Remote download push notification received");
    [AFHTTPSessionManager_Instance downloadFile:completionHandler];        
}

[2] Start a new download Task

- (void)downloadFile:(void (^)(UIBackgroundFetchResult))completionHandler {
    NSURLSessionDownloadTask *task = [AFHTTPSessionManager_Instance downloadTaskWithRequest:request progress:nil destination:nil completionHandler:nil];
    [task resume];
    NSLog(@"Starting download of %@", request.URL.absoluteString);

    // Some additional time to start the download
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 2 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
        NSLog(@"Completion handler!");
        completionHandler(UIBackgroundFetchResultNewData);
});

[3] Handle the download

[self setDownloadTaskDidFinishDownloadingBlock:^NSURL *(NSURLSession *session, NSURLSessionDownloadTask *downloadTask, NSURL *location) {
  NSLog(@"Download complete!");
  // ... Create save path
  return path;
}];

This results in a log like this:

2015-09-21 15:38:57.145 App[315:20933] Remote download push notification received
2015-09-21 15:38:57.485 App[315:20933] Starting download of http://domain.com/file.mov
2015-09-21 15:38:59.654 App[315:20933] Completion handler!
2015-09-21 15:39:06.315 App[315:20933] Download complete!

But sometimes (completely random) I see logs like this:

2015-09-21 15:38:57.145 App[315:20933] Remote download push notification received
2015-09-21 15:38:57.485 App[315:20933] Starting download of http://domain.com/file.mov
2015-09-21 15:38:59.654 App[315:20933] Completion handler!

In other words the download never completes, it looks like the app freezes its background session. Because when I put the app back into the foreground the download will finish at some point.

Has anyone seen this behavior before?
FYI: I enabled the right capabilities, used a correct provision profile and the app has permissions to run in the background.

Update: We've used answers/comments in AFNetworking 2.0 and background transfers when developing the background manager

You are calling the completion handler upon starting download! I'm pretty sure you should call the completion handler when the download is finished not 2 seconds after download started! in other words, you should call completionHandler(UIBackgroundFetchResultNewData); inside self setDownloadTaskDidFinishDownloadingBlock... and of corse pass the CompletionBlock somehow.

[self setDownloadTaskDidFinishDownloadingBlock:^NSURL *(NSURLSession *session, NSURLSessionDownloadTask *downloadTask, NSURL *location) {

  NSLog(@"Download complete!");
  // ... Create save path
 NSLog(@"Completion handler!");
 completionHandler(UIBackgroundFetchResultNewData);

  return path;
}];

The correct log should be something like this:

2015-09-21 15:38:57.145 App[315:20933] Remote download push notification received

2015-09-21 15:38:57.485 App[315:20933] Starting download of http://domain.com/file.mov

2015-09-21 15:38:59.654 App[315:20933] Download complete!

2015-09-21 15:39:06.315 App[315:20933] Completion handler!