At this point I understand your main issue is the audio jack not working? I’d recommend trying to burn a fresh image on a separate sd card (if you have not yet, just use the one from the Pi that’s working fine) and checking if the playback still doesn’t work. If this is the case, your audio jack port might just be faulty.
However, behaviour like the audioplayers not being able to be properly shut down and somehow autostarting despite it being unticked indicate that your system might also be impeded by further issues stemming from your customization.
My general recommendation would really be to burn a fresh image. As mentioned you can create a backup of your current one through various channels (burner software, our burner plugin, etc.)