Looking for help understanding why setting audioSession.setActive(false) in the delegate function speechSynthesizer(_:didFinish:) always fails in the sample below.

import Foundation
import AVFoundation

class Speaker: NSObject, AVSpeechSynthesizerDelegate, @unchecked Sendable {
    static let shared = Speaker()
    
    let audioSession = AVAudioSession.sharedInstance()
    let synthesizer = AVSpeechSynthesizer()
    
    override init() {
        super.init()
        synthesizer.delegate = self
        try? audioSession.setCategory(.playback, options: [.duckOthers])
    }
    
    func speakChat(text: String) {
        let utterance = AVSpeechUtterance(string: text)

        utterance.rate = 0.5
        utterance.volume = 1.0
        try? audioSession.setActive(true)     
        synthesizer.speak(utterance)
    }
    
    func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didFinish utterance: AVSpeechUtterance) {
        do {
            try audioSession.setActive(false)
        } catch {
            print(error.localizedDescription)
        }
    }
}