App / iOS crashes with “Terminating in response to

I have an app which is crashing with

Terminating in response to backboardd's termination

Here the app crashes and even the Springboard. You can see the Apple logo for a short time and it seems that the device is rebooting.

This is taken from the device log

Incident Identifier: AECC8A4C-B6E0-47B5-A2DD-C3A367107087
CrashReporter Key:   26d2ecafff1bd02c1e774f056b3d20c8b03241c3
Hardware Model:      iPad4,2
OS Version:          iPhone OS 7.1.2 (11D257)
Kernel Version:      Darwin Kernel Version 14.0.0: Thu May 15 23:17:54 PDT 2014; root:xnu-2423.10.71~1/RELEASE_ARM64_S5L8960X
Date:                2015-08-17 16:49:06 +0200
Time since snapshot: 117 ms

Free pages:                              114466
Active pages:                            5397
Inactive pages:                          67177
Speculative pages:                       258
Throttled pages:                         0
Purgeable pages:                         0
Wired pages:                             52014
File-backed pages:                       43687
Anonymous pages:                         29145
Compressions:                            4016283
Decompressions:                          516269
Compressor Size:                         10655
Uncompressed Pages in Compressor:        30459
Largest process:   backboardd

Processes
     Name                    <UUID>                       rpages       recent_max   fds      [reason]          (state)

CloudKeychainPro <0b4f59ba89df38039892ce8ad342a013>          152              152  100                      (daemon) (idle)
    syslog_relay <1dc57ae8a60c3654bbf327c16a01d551>           88               88  100                      (daemon) (idle)
storebookkeeperd <83b2723af35f32b3beafb32abd677b7b>          509              509  100                      (daemon) (idle)
            adid <707928b1d97336d5beb5291562421efd>          130              130  200                      (daemon) (idle)
      aosnotifyd <6e3b66f6dad73af08e7f49db92efc045>          559              559  100                      (daemon) (idle)
        installd <4e0b7c36602737a3b0dd0bd733eb4378>          195              195  100                      (daemon) (idle)
    mobileassetd <8574a112afc337638edcd9ac0404f1c6>         1531             1531  200                      (daemon) (idle)
           gamed <943623c4259f306e93b97ce614edf89e>          785              785  100                      (daemon) (idle)
            afcd <208713527dc0315a9198e99db64d3cf1>          119              119  100                      (daemon) (idle)
           timed <294a840542e13dca88162e0fbe687f94>          244              244  100                      (daemon) (idle)
         keybagd <92fe9694044a3f4387459afb0f88a705>          114              114  100                      (daemon) (idle)
MobileGestaltHel <f20bac36fcac32628ad30c2da33effd8>          161              161  100                      (daemon) (idle)
            geod <fb5d1b37f6703663818bd883ed500ea6>          263              263  100                      (daemon) (idle)
softwareupdatese <5cfe93434a573beeb6ef41304af4a352>          949              949  200                      (daemon) (idle)
         assetsd <fd2bd931098b341f846302c614cc5ae8>          471              471  200                      (daemon) (idle)
IMDPersistenceAg <9bd313f498a13e61b54d2ae6ec19ea2c>          220              220  100                      (daemon) (idle)
       accountsd <ee22a71a12f933179729608a16b45094>          622              622  100                      (daemon) (idle)
    itunesstored <3768d425f2103c209fdd1722b8f5acaa>         1171             1171  100                      (daemon) (idle)
       securityd <d79d9800981f3cedad0ca6975c9b9f0c>          602              602  100                      (daemon) (idle)
    mediaremoted <336797e58ac036298bdcdd5d558c227c>          245              245  100                      (daemon) (idle)
coresymbolicatio <0b798227409d39c3b23e63bf4bcb820d>           89               89  100                      (daemon) (idle)
         DuetLST <06955a348ea2371e8d7ec43936431caa>          452              452  100                      (daemon) (idle)
        sandboxd <e75c30438fb73c20a67dd096f80352e3>          130              130  100                      (daemon) (idle)
networkd_privile <5bd47a1c3d12302ea6d78a52cf4ab0a4>           90               90  100                      (daemon) (idle)
        routined <6dbb51d76fbb3d79aa6ea9f3c16c608f>          383              383  100                      (daemon) (idle)
             lsd <f2a08944163c31b9a8fd7f3a43ceacb0>          261              261  100                      (daemon) (idle)
      assistantd <5b53d51bff1236baa617758c37d4f862>          418              418  100                      (daemon) (idle)
            xpcd <8b704605eb243a10bfe026138c1908cd>          292              292  100                      (daemon) (idle)
      librariand <c8d851b111f0324e8de6eaf46ac108d0>          380              380  100                      (daemon) (idle)
      MobileMail <f359afe7da513629b0a6b8aa32a0b90b>         1073             1073  100                      (resume) (continuous)
            tccd <e37a9bd3403c34adbbd9d75e9022240a>          179              179  100                      (daemon)
             kbd <2669fa0ab11a356fbd9482881637e730>          595              595  100                      (daemon)
         MyCrashingApp <25870f37b79d36e584a2e7c6db2717f5>       176783           176783  100  [per-process-limit] (frontmost) (resume)
            ptpd <606d697050af3b23a54e4d75eafef6c0>          605              605  200                      (daemon)
identityservices <1695cbd72da83c4c87c568bd53a01d24>          442              442  200                      (daemon)
           wifid <c0ed3dbc8d7f329489a04faf460c027c>          411              411  200                      (daemon)
         syslogd <88667a0c3dc6398e9b1c6a0c5a5d8f24>          187              187  200                      (daemon)
          powerd <1a8551a962783aa9899be0e55a9c1e58>          152              152  200                      (daemon)
       locationd <3480b01585f039ca9c45ecc16928d8b0>         1139             1139  200                      (daemon)
         imagent <5a1a726d45e033f2bea34c3ae04e817c>          300              300  200                      (daemon)
     dataaccessd <ae41b26410e3338ba33e337fb5439069>         1131             1131  100                      (daemon)
            apsd <f96e01aab90637b0822aff105bf78d70>          578              578  200                      (daemon)
    mediaserverd <6c2cee9548813cea95bf5548d3411408>         1087             1087  100                      (daemon)
   iaptransportd <009cdd0e53bf34829b6a8b69e0ca49bf>          260              260  200                      (daemon)
   mDNSResponder <090a345fd6e13f52b156a3eb9a0e78ee>          220              220  100                      (daemon)
        sharingd <63eae5785eac326987c89d771258ebf8>          571              571  200                      (daemon)
     SpringBoard <ccb584e84f2f3005a9c20897fdb783dd>         6419             6419  100                     
      backboardd <3085386f5f99357aa9f055e0fb79b827>       181876           181876  100  [per-process-limit] (daemon)
       fseventsd <8b8df4c7b46b3dcfb4e1b1d8a6cbb686>         1203             1203   50                      (daemon)
       lockdownd <6bdd33b3920236808292915812d386c8>          344              344   50                      (daemon)
   wirelessproxd <41e0cf822ff33124b3c3949cedce7fd2>          196              196   50                      (daemon)
         configd <2123dc8c1e103375aec0905809a8d38e>          646              646   50                      (daemon)
      aggregated <178824f7adc231249e9e341c03c36855>          590              590  100                      (daemon)
    fairplayd.A2 <9948545906083ff9962c310943eb34de>          148              148  100                      (daemon)
        BTServer <5540f7e4ecd535b9a48b50258130dbd1>          404              404  100                      (daemon)
       distnoted <a237d6a85cae3c409b914ccb8e5b63f1>          182              182  100                      (daemon)
  UserEventAgent <f9cb9c166628392a9d190acff16950b9>          995              995  100                      (daemon)
filecoordination <4d26113e2e3d3b21832eb866679edf38>          251              251  200                      (daemon)
    itunescloudd <266cb30204a039d5b2f5aba30cf05015>         1044             1044  100                      (daemon)
         DTPower <79ced86c61333b6aaa2460276eb0b8eb>          282              282  200                      (daemon)
             ubd <b54681e3319e36b48148ab2026ebf542>          655              655  200                      (daemon)
     eapolclient <a5ac733ff23936b4ab05dde3fd5fb17b>          173              173   50                      (daemon)
            afcd <208713527dc0315a9198e99db64d3cf1>          134              134  200                      (daemon)
notification_pro <293150329f1d317c99a6c5fa2e25963a>          140              140  200                      (daemon)
      DTMobileIS <100bfdacf0a63ae9ab08b27669042812>         2292             2292  200                      (daemon)
       LeakAgent <30856ea2089a3263aaf27fd9faee406d>         3520             3520  100                      (daemon)
        networkd <7262086478d63812ae40c561e8e1acbf>          509              509  200                      (daemon)
WirelessCoexMana <1e096a90f671399d975e83beb668eb91>          151              151  100                      (daemon)
     touchsetupd <9d37501e59f13ca1b1577435bdb43a9f>          197              197  200                      (daemon)
      CommCenter <e5c6b5b1f64833de93bd22bbe135c9b6>         1196             1196  100                      (daemon)
         notifyd <1d555aa3d08c336294a38d9c134dca00>          319              319  100                      (daemon)

**End**

I can't see any hint where the problem lies. The app crashes when I push a new view controller on the navigation stack. On this view controller there is a full screen label. The error also happens after opening and closing the view controller 40 times or so.

Similar questions have different hints:

Too much memory from OS requested
Too many animations/didn't queue animations
Use instruments
Memory warning

So the memory management problem is the most likely one. I tried to use Instruments, but Leaks didn't give me some useful hints (only some malloc and auto release pool with 48 kB max. - seems a OS bug). Also Zombies and Activity Monitor aren't helpful. Using Instruments makes everything really slow.

Only with allocations I saw the UILabel subclass is taking too much space. Every time the new view controller is created, the memory increases by 10 MB (persistent bytes) and that is only the label!

Too make things more complex I'm using Xamarin.iOS. The garbage collector isn't deallocating the view controller when it popped off the navigation controller. But it does it at some time. I think when the system needs more space (nothing left) than the GC kicks in. I could reproduce this behavior in a simple project with my big sized label.

Why does the garbage collector doesn't kick in? I get memory warnings but I can't release something. Normally the view controller and its subviews should get deallocated when they are unloaded from the navigation controller.

When I know why my app is crashing I can do something against this. How can I debug this issue?

Edit:

Now I tried to crash the app on an iPhone. Here you can find the debugger output and here the device log. Again it seems that I'm running out of memory. But my only hint is still the label, because none of the tools can tell me exactly where the problem lies.

I made the following steps to reduce the memory pressure:

used separate class for my custom EventArgs (before: in view controller)
no anonymous function for button in UINavigationBar
no anonymous funciton for UIActionSheet
rewrote EventHandler in that way that I subscribe to them in viewWillAppear and unsubscribe in viewWillDisappear (most of the time)
added Target for UIGestureRecognizer in viewWillAppear and removed it in viewWillDisappear
removed cycle between view controller and datasource through using a WeakReference

I made some checks and it now seems to work. For testing if a view controller is deallocated or not use this:

protected override void Dispose (bool disposing)
{
    Console.WriteLine (String.Format ("{0} controller disposed - {1}", 
        this.GetType (), this.GetHashCode ()));
    base.Dispose (disposing);
}

Through this and commenting the things out I were able to detect the reference cycles. I hope I fixed all problems. The main problems were the EventHandler.

For solving my issue the following questions belong to it:

Clicked handler not executed for UIButton in UIBarButtonItem
How to break reference cycle between view controller and data source
Through presenting new view controller viewWillDisappear on parent is triggered where I unsubscribe from the events
RemoveTarget from UITapGestureRecognizer
Add/remove EventHandler for UIBarButtonItem

The following links were helpful in resolving the memory issue: