As far as I understand it, once you set it up, you have to decide on what distance you focus. Then you have to live with that decision while you are away. The lens is not supposed to change focus unless you ask for it. Unless you can set it to some permanent auto-focus setting.
The problem you are facing atm is exactly what I fear to run into, if I would buy a wide aperature lens with a long focal lenght: An extremely narrow depth of field. I don't quite see the advantage yet.
Given that this thing isn't bargain basement and not exactly working to satisfaction, I'd consider returning it too.
As an alternative to get rid of the problem seen, you could clean up your garage...