But it's not random in the sense that some members don't have to work very hard to see the problem. I tried a lot of combinations but couldn't make my Mini 4 Pro oscillate.
I just experienced this oscillation briefly, about 5 or so up and down swings, flying backwards at full speed, no appreciable winds. It might have continued but I had to stop (about to fly over people).
It was very odd, and would have freaked me...