title: iOS Speech-to-text AVAudioInputNode(?) random crash
body: <p>I have a speech-to-text function in my app, press &amp; hold the button; a viewcontroller is animated from outside windowbounds into view and recording starts, release the button; recording stops and view is animated out of windowbounds.</p>
  
  <p>Suddenly I'm getting some crashreports via Firebase Crashreporting that the function is crashing on some users (2 users / 5 instances, all the same incident).. Below is the code where my crashlog-events points me to.. BUT, I simply can't reproduce the error, I've tried maybe a 1000 times, stressloading (monkey-button-mashing it, etc.), it won't crash on my device.. </p>
  
  <p>Can anybody help me dissect the stacktrace in the bottom / advice? / have suggestions as to what is going wrong? what I can do to stabilize?</p>
  
  <p>To my understanding it revolves around the installTapOnBus:0? Any suggestions for next step?</p>
  
  <pre><code>_audioEngine = [[AVAudioEngine alloc] init];
  _speechRecognizer = [[SFSpeechRecognizer alloc] initWithLocale:[NSLocale localeWithLocaleIdentifier:@"da"]];
  [_speechRecognizer setDelegate:self];
  _request = [[SFSpeechAudioBufferRecognitionRequest alloc] init];
  
  
  AVAudioInputNode *node =[_audioEngine inputNode];
  AVAudioFormat *recordingFormat = [node outputFormatForBus:0];
  
  
  [node installTapOnBus:0 bufferSize:1024 format:recordingFormat block:^(AVAudioPCMBuffer * _Nonnull buffer, AVAudioTime * _Nonnull when) {
  
          [_request appendAudioPCMBuffer:buffer];
  
      }];
  }
  </code></pre>
  
  <p>StackTrace:</p>
  
  <pre><code>1 CoreFoundation __exceptionPreprocess + 1232864
  
  2 libobjc.A.dylib objc_exception_throw + 34100
  
  3 CoreFoundation +[NSException raise:format:arguments:] + 1232560
  
  4 AVFAudio AVAE_RaiseException(NSString*, ...) + 78280
  
  5 AVFAudio AVAudioNodeImplBase::CreateRecordingTap(unsigned long, unsigned int, AVAudioFormat*, void (AVAudioPCMBuffer*, AVAudioTime*) block_pointer) + 554488
  
  6 AVFAudio -[AVAudioNode installTapOnBus:bufferSize:format:block:] + 545144
  
  7 shoppinglist 4295363296 + 297696
  
  8 shoppinglist 4295358408 + 292808
  
  9 UIKit -[UIViewController loadViewIfRequired] + 65212
  
  10 UIKit -[UIViewController view] + 64152
  
  11 shoppinglist 4295296168 + 230568
  
  12 shoppinglist 4295272504 + 206904
  
  13 shoppinglist 4295266368 + 200768
  
  14 UIKit -[UIViewController _setViewAppearState:isAnimating:] + 162800
  
  15 UIKit -[UIViewController __viewWillAppear:] + 162144
  
  16 UIKit __56-[UIPresentationController runTransitionForCurrentState]_block_invoke + 3540196
  
  17 UIKit _runAfterCACommitDeferredBlocks + 2738508
  
  18 UIKit _cleanUpAfterCAFlushAndRunDeferredBlocks + 2681320
  
  19 UIKit _afterCACommitHandler + 9796
  
  20 CoreFoundation __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 895396
  
  21 CoreFoundation __CFRunLoopDoObservers + 886316
  
  22 CoreFoundation __CFRunLoopRun + 887416
  
  23 CoreFoundation CFRunLoopRunSpecific + 36256
  
  24 GraphicsServices GSEventRunModal + 49264
  
  25 UIKit UIApplicationMain + 479316
  
  26 shoppinglist 4295262124 + 196524
  
  27 libdyld.dylib start + 17816
  </code></pre>