That was implicit on my remark about key users, meetings are not always about being seated around a table.
Actual users engaged and discussing how they actually work and what they, the actual people that have to deal 8h a day with the system, want it to behave.
These same people will dismiss their previous remarks and state that the old way was better, even though they were the ones actually suggesting the new behaviours as improvements to the current issues.
That why good user research is not about asking customers what they want, but rather observing them use products, identify the pain points that are obvious and ask them more questions to understand better their problems and desires.
This is exactly what I mean. Also it's best to observe them during high stress periods when they are busiest. The pain points will jump out at you in those situations.
Managers especially fuck this up. Go straight to the source and see what the people who will be using your app do.