human factors
As with any job you are correct human factors come into play quite alot with automated loadsheets.
There have been more than one (hundred) occasions in my career when airlines and systems maintainers (or whatever you want to call them) do not keep systems updated. Ok it is a necessary requirement that the weights are checked before any loadsheet is produced but at what stage do you rely on the printed matter from the airlines or that i the system.
A certain main operator never sends us updated weights we just rely on the ones provided in their automated system.
another operator sends updated weights every other day and we never know when they are in use or which issue we are to be using on which particular day. Another provides us with weights but never sends them to the systems people so we have to change them manually every day!
You'd think it would be a slightly more serious matter.