So I had a PC crash while watching Netflix in fullscreen on my second monitor - Luckily, Session Manager had managed to save my session soon before the crash.
However, when I restored it, the window with the fullscreen Netflix tab restored as a blank white box, which couldn't be interacted with. Audio from the Netflix video was still playing, but nothing was visible aside from the white box. The only way to get rid of it was to select the window via the Windows taskbar, and then Alt + F4 it to close it. Subsequent attempts to restore the window as a whole had the same issue. All other windows were okay, and I could Alt + Tab to them without a problem.
The only way past it was to restore the session, close the affected window with Alt + F4, open a new blank window with Ctrl + N, open up Session Buddy in that window, go to the saved session, then right click the affected window and choose "Open Tabs" to restore the tabs from those windows to the new blank window.