I've got a similar problem. It seems that AVSpeechSynthesizer does not work well with Address Sanitizer. I spent a lot of time trying to figure this out. Terrible experience! Don't want to believe that the Apple engineering team left this problem unsolved for a year. For a temporary solution, can they just turn off the Address Sanitizer for AVSpeechSynthesizer?

Have you tried to re-access the attributedText without using the DispatchQueue? I have some similar problems with UITextView.