Cant turn down the system

[Flavor]

sometimes it does work without any problems

Do you mean that sometimes the power switch will properly shut down the system? If so, then maybe it seems like something is killing the shutdown script.

The other (odd) thought it that MAYBE the slider isn't sliding far enough. I do know that some people have said that they have to shave off a bit of plastic to allow the slider to travel all the way over to register. Do you have to push it a little hard to get it to turn on the machine?