Implementing Loreta inverse method

Hi

I've tried to implement the Loreta inverse operator with an MNE volume source space, as in the following listing:

   https://gist.github.com/maedoc/12f04151292f0fe6fad0

Unfortunately, the resulting operator projects only to one corner of the brain (see image attached to listing).

This particular BEM was previously used with MNE to produce a localization that converges with other results from Brainstorm, themselves confirmed by clinical observation, so this should not be the source of the problem.

I believe I've not understood well enough how MNE represents foward and inverse operators which is why I'm asking for a bit of help on this subject.

Thanks,
Marmaduke