OK @Walks_At_Night You're a tech guy, right? Sort of?
@KSM Guess it depends on your definition of tech guy. I've received a paycheck for writing code in 5 distinct decades now but believe me when I saw that there is a whole lot more on the "I don't know" side in that arena as opposed to the "I do know" portion.
Regarding your question. Can you remove the Side 1 from the media player and re-add it? Do you a copy of the file saved off somewhere? Maybe it got corrupted in the media player. If you have the file saved off elsewhere, try playing it in VLC - if it plays fine it is probably in good shape for the re-add attempt.
P.S. Kudos if you are trying to learn Mandarin.