I have a second monitor that I occasionally plug in and enable via xrandr. On the second monitor is a panel with Window Buttons, which has "Show windows from all monitors" disabled.

However, when I enable the second monitor, Window Buttons will only show windows from the first screen, until I enter the options and enable, then disable "Show windows from all monitors" again. At this point, it will correctly show windows from the second screen, like it's supposed to.