How quickly are you lifting the seat when you get up? If you hesitate for just an instant between taking your weight off the seat and taking the seat off the safety switch it will result in the engine dying. I grab the back of the seat and lift it as I rise from the seat all in one fluid motion.
Well it turns out my "Seat Tilt Switch" was bad. I tested it according to the WSM and found out it wasn't working. I ordered a new one (pricey thing too) and installed today. Now it works like it should when engaging the stationary PTO. Problem solved.