There has to be a D and R at each station to insure no shenanigans. The exception is there is only one inspector.
The day of election is more the problem. The vote center might well be staffed by people who work in the office. But day of requires a lot of people, people who show up after just the 2 hours. Now some may have worked previous years, but not all.
Even at the center theyake mistakes. The HT has an article about a student voting Day 1 being told he could not vote. Turns out he was a legal voter. In addition, he should have been offered a provisional ballot and wasn't.
There are a lot of questions that come up. Can person X help me vote? I moved yesterday, where do I vote? Is this an appropriate ID? When we used to have machines, how to know they were working. When we had paper ballots, if the form says use an X, is a checkmark allowed?
At some point election day, a list of names will be read off of people who voted remotely (probably absentee) after the poll book was sent out. The clerks have to go in and mark people as having voted. I will suggest that somewhere in the state someone is marking the wrong line.