This is a different issue – there haven’t been any reported circumstances where there is 0% CPU use but a stuck process, or a process which is in some way “stuck” but also responds to app interaction as you described. I’d guess it is due to something misconfigured, changed or unsupported in the audio session, or it is due to something else about the app that is happening in the same timeframe such as use of a different media object which is changing (and breaking) the audio session. There is probably information for you in the logging.
One probable issue here is that your language size is approximately 5x-20x (depending on word selection) larger than the maximum vocabulary size, which will affect search times.