So I am now wondering if it is anerobic fermentation.
The second bag I found distasteful was double fermented and I am wondering if the first was a Rwandan anerobic which one of the suppliers I have used see. They say anerobic fermentation causes lactic acid acid which could well account for the sour milk vibes I was getting.
I am going away for a month and wanting to take a couple of bags of coffee with me, so have ordered a Monsoon and a summer blend to keep me going :)