Hugues,
My focus distance for the black & white vertical lines is about 43cm, definitely not 50cm like your black cross.
My scanner and turntable are wired up via USB sockets in the wall at the other side of the room. I haven't disconnected the turntable in Free-scan, I just select the option on screen!
That might explain it then.
Just updating Parallels and then I will test what distance my black cross is in focus.

Mike