The left and right parts on the top of the lower window have broken due to age. These are the parts that have the small spring mechanism to keep the window. In line as it moves up and down. The photos may be misleading in the they make the parts look like they are vertical rather than horizontal on top of the bottom window. Included are left and right pictures from a similar window showing intact parts. One of the damaged parts photos shows the entire part removed and the other shows just the opening where the slide control should be.
The fifth picture is of the security piece that keeps the window from opening all of the way if you want some air. That too needs replacement.
