How does AudioSource.priority work?

I need some detailed information on the conditions for when an AudioSource should play a sound.

Some times when the profiler is reporting that there are ~22 AudioSources around, some sounds still are still not heard.

I thought that there was a hard limit of 32 AudioSources, and that the 32 AudioSources with the lowest priority number would be heard.
Some times when I have ~35 AudioSources, and I play sounds that have a low priority number, it's still not heard (I was playing in the editor). I know that at least 8 AudioSources had higher priority numbers at that time.

These problems also vary from execution to execution. Some times it's fixed by stopping and starting the game, then doing the exact actions as I previously did.

Is there an effective way of debugging issues about missing sounds?