My 7.5 failed to change up once.
I was on a country road with the whole family in the car. Kicked down into 2nd, moved out to overtake a lorry, accelerating hard then the power disappeared. I looked down and the revs were at about 7k. Lifted off and it found a gear. Luckily I had built up enough speed to tuck in past the lorry.
My wife had her hands over her eyes.
Never happened again.
Think very occasionally these boxes can do odd things.