Hi Van,
The position of the person which the user is trying to access is not a default position, also I'm not sure why this was set to '9'. It was set as so a long time back, and ideally it should be 1 or 2 or 3 or 4. I'm not sure what would be the impact when it is set to '9' but I guess that is not the problem here because it was set as '9' a long time before and these group of users are facing this problem only since last week.