It's a long time that with the latest version (I don't remember when it started) that qB stalls, and its process is still visible in the Windows 7 x64 Windows Task manager when you close it, either by File->Exit or by Alt-F4.
I always have to end the process in the Windows Task manager, or use taskkill.
That's annoying enough that I dropped on my desktop a .bat file with:
TASKKILL /F /IM qbittorrent.exe /T
to do it more easily.
Any way to avoid that problem?