You only play one mp3 at a time, correct? Therefore you only need one Player!
I think the issue might be that there is inaccuracy in the volume setting (50) - you could add a slider for the User to set the volume.
Also, you don't need all those buttons - a List View can do the same job, better.
How did you arrange the buttons? Did you use a Table Arrangement? That is something else that might cause the issue, it is very easy to corrupt the file with a placement error in that Arrangement.
That's a lot of Mp3s stored in the App Assets (Media). You might want to consider storing them in the ASD (App Specific Folder) so the App is not too big.
Here is a basic example that you can try with your mp3 files: PlayerMp3.aia (2.6 KB)
size of bigger file is 2.3MB, total app size is 24MB
I made all these button because this app is for an old man and he is not friendly with smartphone (and slider)! He only would need to touch the button and the music starts
Yes, I used table arrangement, but also if i place the button without table arrangement (vertical placement), it doesn't work.