Netflix original audio for a show not kept in saved phrases

On Netflix (UK), for show “Falling Into Your Smile”, for saved phrases, am finding the original audio is lost and replaced with machine audio. I’m using audio “Mandarin [Original]” and tried with subtitles “Mandarin [Original] ASR” and “Chinese (Simplified)”, seems like the saved phrase doesn’t get the right timestamps, so when I listen immediately after saving the phrase it has original audio but the audio doesn’t necessarily match the phrase. Later on, it gets replaced with machine audio. When I tried with a different Netflix show, it seemed to keep the original audio.

I assume this isn’t expected?