Earlier today, Stephen streamed himself recording some episodes of First20, including Terraria, Dicey Dungeons, Disco Elysium, and Horizon Zero Dawn. However, when he was recording himself playing Horizon: Zero Dawn, stream viewers noticed that there were some audio problems. He listened to the audio after the stream, he noticed that the audio was jittery, "like a CD skipping". He thought that the locally recorded version of the stream would be fine. It wasn't.
All of this stems from multi-track audio recording, a feature in OBS that Stephen's been trying to use. This makes all audio better for the stream. Most people don't use this, but Stephen does. He's going to do his best to get this issue fixed for future streams.