I've been testing some possibilities and I think I found what causes this bug.
It's about when you make some modifies to the audio folder while you using Spine.
I've recorded a video, but it's too big to upload here.
I use a web to modify .mp3 and download the sfx directly to the audio folder. When I do that, it's when Spine's audio gets bugged.
I've send an email to contact@esotericsoftware.com with a .rar containing the video
Thanks for the video!
It definitely looks like a bug that the audio plays even though you deleted the key. However, I tried it and the audio stops when I delete the key. I'm not sure what would be different about what you've shown.
One thing that stands out is your audio file seems to have a long duration. The duration is shown by the horizontal purple line in the dopesheet. It seems like the audible part of your sound is relatively short, but the audio file is very long. I tried with a long audio file too, but still was not able to reproduce it.
If you can reproduce it every time, we would appreciate if you can send your project so we can see the problem firsthand. contact@esotericsoftware.com
The long audio will be replaced by a shorter one in loop, I always cut the audios to not overpass the last animation's frame. But I don't think this is the issue, because I get the bug with shorter audios too.
Maybe it's just a pile of circumstances (audio folder in Unity, working with GitHub, modifying audios through a web...) and it seems hard to reproduce from zero.
I'll let you know if I find out something else that could help.
Longer video showing a little bit more of the bug.
In this video, we can hear the sounds from the previous video I uploaded (waterpool).
Notice that at the beggining, it sounds a water sound between all the other sounds. Then, when I create 3 Events based on the sounds "sfx_water_pool", the bug with this sound ends. But it doesn't happens the same when I create the event "sfx_woosh1" and "sfx_water_softsplash".
Maybe you @Nate were correct with the duration of the sound (going beyond the last animation frame).
And btw: when I try to select multiple event keyframes, it does something weird and doesn't let me select more than one. (00:19 on video).
There shouldn't be a problem with the duration passing the last key. You can turn off repeat to let it play. At runtime typically once sounds are triggered to start playing, they play to the end no matter what the animation is doing.
Audio not getting unloaded is bad. I imagine it's hard to work like that, and eventually it may have a ton of audio loaded that it shouldn't.
It seems to happen in your project pretty easily. If you send it, we'll keep it private. You can exclude the images, we only need the .spine file and audio files. Maybe only 1-2 audio files.
Edit: saw your email with the video. We'll try adding/removing/editing audio files in the audio folder.
I'll send the .spine with the images and the sounds from the last video via email (contact@esotericsoftware.com)
Thanks for answering so fast and putting all that interest, like always!
Thanks!
We fixed not being able to box select.
We found when the timeline is playing and a key is clicked, the timeline position changes but the audio doesn't use the new position. This ends up playing audio events at the wrong time. Also fixed!
We haven't been able to reproduce the sounds still playing after the keys are deleted. Maybe something that happened before your video caused that for just some of the keys. In your video after you added the 3 pool sounds, you deleted them and they no longer play, so some of them are working correctly. This part is still a mystery! 
If you restart Spine does the audio stop playing correctly after deleting keys? If so then I guess keep an eye out for what might trigger it to not unload audio.
Nate Oh nice to hear that issue related to box selection it's fixed!
Yes, when I restart Spine, the bug with audios disappear, at least until it appears again when I switch to other project or something related to any modify at audio folder.
It's hard to find out what causes this bug exactly. If I discover anything, I'll come back here.
Thanks! Have a great day!
