Doesn't work either on Windows 10 1709

I just downloaded 7307, and I can confirm that the issue still happens. Doesn´t occur with WX.
I'm very inclined to believe you since 3 people reported it to me as broken now but I just can't reproduce it at the moment. Making it very hard to debug and fix :/
Edit: Please try the latest master, I can't guarantee that it fixes the issue but it might just work.
Looking closer it seems that the people mean the
main window (where you select games) and not the render window (where the game is displayed and what spycrab tried to "fix"). I tried to add that functionality in
PR #6802. Edit: Got merged unexpectedly quickly into
5.0-7342.
Using 5.0-6854 and it STILL does not save last window position (main game select window).

Fine on non-qt version.
That build is kinda old at this point. Use 8516 instead.