I got a regular senate mid season last year and got 2 OTF, one ending my season with a concussion. It was free skiing, pretty much exactly as you described, crossing the second wake. The way I was analysing it, I was crossing the wakes with too much tip out of the water, so when I was going down that 2nd wake it was grabbing the tip and sending me over the bars.
I have then moved my binding to 30" from the tail, and took one degree out of the wing. The ski ride a lot more level to the water and its noticeably faster than before.