I am not sure or if I remember reading anyone having this issue. I do remember reading on the other Duo thread some users were initially grinding at lower grind sizes, and re-zeroing helped.
This might probably an isolated incident. We know it doesn’t take anything from Niche Duo. It’s a great grinder - it is simple, has got a lovely workflow, it just works and the customer support is fantastic.
Unless cost is an issue for me, I wouldn’t buy anything other than this if I were to buy again. In fact, my daughter needs a grinder. She has taken my hand grinder as a temporary set up.
IMO, I see a little point in paying almost £400 for a few years old Zero. One may as well pay a little more and get a new grinder, which is precisely my dilemma - Zero or Duo for more money. :-)
Bottomline - you won’t regret buying the Duo, IMO. :-)