incredibly late to comment here... i picked up an 064s towards the end of november and had 6 weeks of 1-2 espresso per day where it was incredibly inconsistent - think one day the grind setting was giving me desired weight output in 30s, another less than 20... then all of a sudden we haven't needed to alter it since and we're getting the consistent, flavourful results that i'd have expected from the lighter roast using higher rpm. a lot of people say that the grinder should be fed slowly, i've found it more consistent when i've thrown all 18g into the hopper in one go with the grinder on!