Sash window meeting rails not even
First it looks like the windows are put in reversed. The glazing putty, the angled places around the windows, have always faced out on old windows. What is now the outside should have a profile something like this



Although while looking for this image, I did find profiles that match what you have there too.

If they are reversed, the angled bottom will keep the window higher in the opening so the middle does not line up. If there is weatherstripping, the groove will not line up. If they are not reversed, and there is weatherstripping around the perimeter, there may be numerous coats of paint on the top and bottom, so the edge does not fit into its corresponding groove anymore, or the metal is bent so it doesn't fit either. More pictures of the frame conditions would help confirm this.