iOS crash logs not recorded on device?

Does anyone know what might cause iOS crashes (not out of memory crashes) to not get recorded?

I would expect to find crash files in the device logs (viewed in XCode Organizer), but this very rarely actually works.

We are able to catch crashes when the device is connected to the debugger in XCode, but this obviously is not very useful when it comes to external QA.

We’ve also tried Test Flight crash reporting. We get sessions recorded and remote debug output logged, but never any crashes. Their support guy said this may be an issue with Unity projects?

Anyone else have any problems with this? Any solutions?

This problem has gone away with the Unity 4.2 update, in which they added a crash reporter. Crash logs are appearing both on the device and on TestFlight. Hooray!