Finding reason why app stopped in background? Some apps such as system statistics loggers or third-party voice recorder apps (used due to additional functionality and formats) may stop in background without the user noticing it.

The user notices it when trying to read the saved data, play the audio file, or open the app, just to see that the data logging or recording has stopped at some point, which diminishes trust into the app.

How do I know the reasons for why the app quit in background, while the phone was not being touched, just placed somewhere?
You can try Logcat Extreme.
Then in the settings prioritise errors.