Had to sit out this year for a variety of reasons, but I've helped to process non-machine ballots several times in the past. All this drama, misinformation, and accusation makes me very sad. Here's my personal experience, FWIW.

*The volunteers who counted the votes have simply been doing their local civic duty. I never met anyone with an agenda other than that.
*People were asked to self-identify by party and always paired with someone of a different persuasion. (Independents, Greens, Libertarians, etc. are a highly valued commodity, because they can "go both ways.")
*Those pairs worked together for many hours, and often became friends. The most satisfying moments come from the most challenging ballots, when reasonable minds come together.
*The culture of the room rapidly becomes supportive, with everyone watching out for each other in terms of tiredness, biological needs, etc.
*The systems for receiving, processing, and storing the ballots was always simple and transparent.
*Observers are always present in some form, but there's really very little to "observe." Paint drying level of entertainment.
*The biggest threat to accuracy is a disturbance to both the process and the culture of the room. Its has a machine-like quality to it, and also critical is the supportiveness and cooperativeness - it kept us all energized and focused.
*In the end, the trust and friendships that developed between counting pairs of different political parties was a small contribution to democracy. I still think fondly of a couple of people from many years ago.

One man's experience, FWIW.