It's likely due to the fact that I had to ship the game using a nightly build of Ren'Py since there is a more prominent audio-related bug in the current stable release which affected this game. Even though you didn't mention which OS you are playing on, I assume it's Android since I do have a small group of Android users who seem to be having the same issues.
When the next stable release of Ren'Py is available, I plan to update the game engine which will hopefully resolve some stability and performance issues for Android users.