Hi, @DAB.
Thank you for sharing your thoughts. I understood it. And I agree with you, we hope for further information. Other threads @sameer posted may be helpful to understand this issue. For some Metformin ER tablets, NDMA formation in long-term and accelerated stability conditions were not observed.
As @ASrinivasan pointed out, the difference of nitrite/nitrate amounts from batch to batch in excipients may play a key role, I guess.