There is an argument between the Mechaber and the RMA O”CH 447:4
if there is something called חוזר וניעור once it becomes botel in sixty until night when chometz is not botel anymore because the prohibition falls on the smallest amount. The Mechaber’s view is that we don’t say that, but the RMA differentiates between liquids and solids. So according to this view you cannot rely on bitul and the machine must be cleaned every 18 minutes in order it should not become chometz and reawaken itself at night once it was botel.
I would like to know if people go after 18 minute machine matzos?
laskern: The Breur’s kehilla purchase Hadar 18 minute Matzos.
Breur used to rent Horowitz Margareten factory for a day to bake 18 minute matzos.
According to the Rambam we should only have cholov yisroel on pesach.