Using xfce4-panel 4.13.3 (Xfce 4.12)

I have a single panel covering the bottom of my screen.

The window buttons on the panel do not expand to the bottommost pixel of the screen, making it impossible to click the buttons unless one aims the mouse very precisely.

In other words, the infinite height property is lost. (See https://blog.codinghorror.com/fitts-law-and-infinite-width/ )

Please make my window buttons clickable again!