I think that this used to work but now it fails. I often have to use the scroll wheel zoom while selecting to make sure that the select window captures the correct objects. If I zoom in far enough that some of the objects are partially off-screen, those objects are not selected. Zoom is working fine at the time; there is no slowing of the zoom.
The simplest way to duplicate this is to create a rectangle and try to window select it. Start with the rectangle on screen but, while selecting, zoom in so that part of the rectangle is not visible, then release the mouse button. The rectangle will not be selected.
I’d swear that this used to work. I apologize if this has already been covered; I have searched but I might be using the wrong terms.