My crash report is below. My hypothesis, based on the error having to do with decrypting encrypted data, is that a certificate or key expired someplace, and iOS's voice library can no longer decode certain voice files. But that really doesn't explain why it is so intermittent. CrashReporter Key:	890f4575948bc41c861ae0f37928bcdd912bd0d3 Hardware Model:		 iPhone10,5 Process:						dvxapp Identifier:				 com.davinix.dvxapp Version:						1.7.0 Role:							 Foreground OS Version:				 iOS 14.3 Exception Type:		 EXC_BAD_ACCESS EXC_BAD_ACCESS: Attempted to dereference garbage pointer 0x11f600000. 0 TextToSpeech							_TTSCreateDecryptedDataFromEncryptedData 1 TextToSpeechBundleSupport -[TTSVocalizer loadResource:mimeType:resourceURL:supportsAccurateWordCallbacks:] 2 TextToSpeechBundleSupport -[TTSSpeechServerInstance _loadVoiceResource:voiceResource:] 3 TextToSpeechBundleSupport -[TTSSpeechServerInstance _initializeSpeechEngine:] 4 TextToSpeechBundleSupport -[TTSSpeechServerInstance _initializeSpeech:] 5 TextToSpeechBundleSupport -[TTSSpeechServerInstance _processCurrentRequest:] 6 TextToSpeechBundleSupport -[TTSSpeechServerInstance _handleSpeechThread] 7 TextToSpeechBundleSupport __SpeechThread 8 libsystem_pthread.dylib	 __pthread_start Edited to add: I was able to resolve this by removing the willSpeakRangeOfSpeechString method from my speech synthesizer delegate, which fortunately I didn't use for anything. To those trying to reproduce, try using the com.apple.ttsbundle.sirimaleen-US_compact (Aaron) or com.apple.ttsbundle.Samantha-compact (Samantha) voice, which gave me the most consistent crashes.