display boxes moving off screen

ok. that has something to do with "stage manager". you will notice a border around your display when you activated. that border will appear any time you click on an empty spot on your desktop. it will move open apps beyond that border, so you can see your desktop items. if you want to stop it from appearing, you can go into System Settings > Desktop & Dock and in the Desktop & Stage Manager section, set "Click wallpaper to reveal desktop" to "Only in Stage Manager"

but I don't use stage manager, so I don't know what happens with stage manager when set that way.

do you have more than one display connected?

what device is this exactly, Mac Pro desktop 42 lb silver tower where your post was placed, or MacBook Pro with integrated display? what model-year and display size?

is this occurring after clicking an empty spot on your desktop? and does clicking again on your desktop have the windows returning to where they were?

I just found this: Organize your Mac desktop with Stage Manager - Apple Support