This is my version of “Trust no one”.
If I had a penny for every user that told me that he did do what I told him to do in order to fix some issue but in the end didn’t, I’d be as rich as Larry Ellison but without all the bad karma.
So trust me (heh), when you are helping someone debugging some issue, try to get visual confirmation or at least ask them to triple check everything or you might waste a few hours. Especially when there’s a lot of moving parts… like distributed systems.