Vinyl rails may not be precisely straight at times. There are a variety of reasons for his, but the composition of vinyl that results in its warmth, its weatherability, and its freedom from maintenance, also allows it to be somewhat flexible. Vinyl sashes and frames must have room to expand and contract with variations in temperature from summer to winter. The insulated glass is made with the highest quality float glass used in the window industry. Grids placed in between the pieces of glass are sometimes not perfectly lined up, either vertically or horizontally.
Air can enter around and through the best window.
Do not expect to have zero air infiltration on any vertically or horizontally operating window. Smart Windows are designed to allow the minimum amount of air infiltration consistent with the ease of operation of your window and consistent with industry standards for allowable air infiltration. Water can enter into the sill track of several different styles of windows. These windows are designed to capture this water before it enters your home and drain it outside. The presence of water in the sill of the window does not indicate a problem.