speakTextAsync SynthesizingAudioCompleted indicator is raised in beginning of audio instead of end

You can run this code and see how it happens:

const speak = async (text, onEnd, pitch = 1, rate = 0.35) => {
const tokenObj = await getTokenOrRefresh();
const speechConfig = speechsdk.SpeechConfig.fromAuthorizationToken(tokenObj.authToken, tokenObj.region);
speechConfig.speechSynthesisVoiceName = 'es-AR-ElenaNeural';
const audioConfig = speechsdk.AudioConfig.fromDefaultSpeakerOutput();
const synthesizer = new speechsdk.SpeechSynthesizer(speechConfig, audioConfig);

synthesizer.speakTextAsync(text, result => {
if (result.reason === ResultReason.SynthesizingAudioCompleted) {
await onEnd(); // This runs in the start of the audio playback instead of in the end.

} else {
console.error('Speech was cancelled or could not be recognized. Ensure your microphone is working properly.');
}
});
}