Delay between video and audio

I’m using the code from this GitHub repo for streaming:
https://github.com/de-id/live-streaming-demo/blob/main/streaming-client-api.js

Most of my code runs on the frontend, while the API calls (including the API key) are handled on the backend. The functions I’m using are nearly identical to those in the GitHub code.

However, I'm running into two issues:

Audio and Video Out of Sync:
When I send a talks request, the video and audio are not synchronized — it seems like the audio only starts playing toward the end of the video.

Black Clip on Second Request:
When I send another talks request in the same session, the player only shows a black screen (no video or audio).

What could be causing this?