If the machines were filling in missing undervotes this could explain why a historic low number of ballots, only 3.2%, had the house race blank. The only other explanation I have found so far is that fraudulent ballots were created with votes all the way down. 3.2% is significantly lower than the lowest percentage in history and it’s even lower still in Georgia, Michigan, and Pennsylvania. (2.0%, 2.2%, 2.9%)