Identify why the device does not disconnect in certain cases where there is an error

[raacampbell]

I have more than once found that on some errors the device is not disconnected, even though the cleanup function ought to do this. So check:

1. Is it indeed the case that the cleanup function isn't running in these cases?
2. Really do we need the try/catch statements? Maybe there is a less nasty way of achieving the same effect.
3. Is there a way of liberating a blocked device? Perhaps a MAX reset? If so, document it.