With my back window, when I press the down/open button, the window will open and stop at the position I take my finger off the button. When I press the up/close button though, it will stay closed if I close it completely, but if I take my finger off the button when its at any other position (eg 1/4, 1/2 or 3/4 way up), it will turn round and go all the way down. Is this normal? It seams strange to me.