As per usual I think I worked it out by trial and error....
I replaced the battery on the McModule with a brand new one and now I can update the firmware on all 3 McModules
. Voltage of old battery was 3.05-2.99v , voltage of brand new battery was 3.3v.
So I suppose programming the FW needs more power from the battery ? Hopefully this thread will help others in the future.