I have been keeping the book for years. I can't tell you the number of times I have had the "he should have had it" - "the standard is ordinary effort" conversation. However, this year, I have become frustrated by a first baseman who doesn't scoop well and never comes off the bag to block a ball. The throws could be better but a better first baseman would have cut the errors in half or at least held the runner at first instead of letting the ball get by him and the runner going to 2nd.
All this to say is that scoring is subjective and sometimes the wrong person is hit with the error (ex. SS makes a great play in the hole and throws off balance. Ball is a low throw that one hops. 1st baseman scoops and misses - E6. But a good 1B makes the play 9/10 times).
When I did some official scoring in pro ball, I wouldn't make a change to my box score unless both managers agreed. Sometimes they would agree but often they would each find a call they wanted changed and both would agree to it.