OK, I am still working on it... Actually, the "problem" is that when I press play (as I wrote manually or automatically) the screen, where I could press stop, just vanishes.
I have just seen now, that sometimes, I can find it "behind" the BiaB screen, but sometimes not.
I think it would be better that the Multiriff screen "sticks" where it belongs... And in case it does by most of you users, how can I change this (strange) behaviour???