Believe it or not, the iPhone can fill with crash logs and make no more.  We recently encountered more than one person that had a crashing app, but no new crash logs were appearing.

The crash information still appears in the device console, but no crash log is created.

Syncing the iPhone with iTunes on a desktop will remove all the old crash logs, then new crash logs can be generated.

Alternatively, you can delete the old logs with Xcode if the device is local and can be connected to USB.

(And boy, has it been a long time since I published here.  I have several items I want to write up.  We will see if time allows.)