I wonder if the position sensor may need recalibration? Don't know how to do that on the i3, but on some cars, you run the window up to the top and hold the button for some additional period of time. A call to the service center might tell you how to do it...I don't remember it being in the manual, but it could be.
As to the windows going done, my experience is that this is almost exclusively a result of pressing the unlock button on the fob long enough. Easy enough to do when in your pocket, depending on what else may be in there. I have comfort access, and bought the fob cover, installed the fob in it backwards to cover the buttons, and it's not happened to me since. If you don't have comfort access, it makes it a little harder to press the buttons, but it can still be done. In my case, the fob rarely comes out of my pocket and I almost never need to push a button, so it's worked out well for me.
