Basically what you do is to put "fences" around dangerous areas as a manager and don't confront them unless it is "too much" - where too much depends on a situation.

That was what I observed when working as developer of a factory control system, while testing I was sitting in place where you basically should not sit ... but I was in control of system so I knew what I was doing. No one confronted me about that, next day there was fence preventing access to that place. First thing I thought was "someone could just tell me", but yeah if you can fix thing without confronting and you have loads of other things to do in a day I totally understand someone rather put a fence than confront some guy he does not really know because he is a contractor.

I can see it is easier to move people to other projects if they don't get well instead of having discussion to make things clear. But such discussion can take too much time and energy from everyone involved.