Hi Gribbstar and thanks for your reply...
Yes, I'm using a Quest 2, but I don't use Oculus Tray Tool...
Anyway, after reading your post I remembered that before playing the mission I had received a warning from "windows defender" indicating that something called "memory integrity" was not activated, so, given that warning, I entered "windows defender" and activated it.
The facti is that after deactivating it again, the mission has worked perfectly and, once I newly have activated it, the mission has had lag and desynchronization problems again, so finally I have left it deactivated, at least until I manage to finish such mission...
Why such thing happens? I really have no idea...