I use a laptop with a docking station on my windows version of Lightburn (ruida controller) . When docked, I have 2 monitors and the preview is set to come up in the second monitor. If I just undock and pick up my laptop without moving the display back to the laptop display I will lose the preview and can not get it back until I redock and manually move it. I have even exited Lightburn and rebooted the laptop, I still do not get it back.
It does this when opening the preview window too, so you don’t have to nuke your whole window layout. If you hold the Shift key when clicking the preview button it’ll use the default window position for it.