Screen Mirroring - Windows Not Duplicating

I've got a Raspberry Pi 4B and two monitors. In the Screen Layout Editor, I have both monitors set to the same resolution and overlaid on top of each other. The mouse, desktop background, and desktop icons are all mirroring properly across both monitors. However, any windows open on my primary monitor (chromium, system settings, etc.) don't show on the secondary monitor unless the window is dragged around with the mouse. If dragging a window, it appears on both monitors. When the dragging stops, the window disappears on the secondary monitor. I've looked through a bunch of forum posts, but no one seems to have this kind of problem. Any advice on how to proceed?