Umberto, this is one of the reasons I check the forum frequently. Mine does this all the time, but ONLY if I use GSX on departure and the subsequent arrival, and then try a second departure. The wing walker glides next to the plane. His legs don't move. It doesn't seem to be related to the zoom, but I'll fool around with that soon. I'm always in VC mode during push back, and at whatever zoom level looks "normal" when looking out of the window. Not too wide or narrow. It happens at the default KBWI, KPVD, KBOS, KATL, as well as at FSDT KIAD, and T2G's KMCO. It happens while flying the default 737 and Airbus.
I've been in the habit of resetting Couatl right after the marshaller walks off. I start the de-boarding process right after the reset. The wing walker works every time when I do this.
Sometimes, I forget to do that so I keep checking here to see if it's been fixed. If ya need a log or something, I'll be happy to send one.