Why does Bachmann reaction differ in batch characteristics as opposed to flow characteristics

I have studied this reaction for over a year and it makes zero sense. When synthesizing HMX from Bachmann reaction, an important intermediate is DPT. DPT is formed by reaction of nitric and hexamine in acetic acid and acetic anhydride with a 60-65% yield. 63% to be precise according to literature. But, there's a caveat. Everyone who runs this reaction adds them simultaneously. All 3 reactants. I added them in steps like 2 together, 1 in a mixture of 2, all 3 together and in a flow setup as well. Adding them not altogether always decreases the yields. Similarly, decreasing acetic acid and acetic anhydride also reduces yield. One would assume Acetic Acid is the solvent and acetic anhydride the water remover in the reaction but even in a flow setup, if you reduce their ratios, the yields go down. Solvents are not supposed to behave in that manner. IF anyone has any experience with this reaction, can they just explain to me what goes on in it?


