As a follow-up, I summarized all the KMix bugs I've run into + my setup and some debugging 
attempts here:

https://gist.github.com/jstolarek/9541d35cded45e593b41ed48aaadc521

That should probably end up somewhere on the bugtracker but I went for easy to read markdown 
formatting.

I wonder whether it would be possible to back-port KMix fixes from testing builds to PSB?

Janek