Fin is on the money here guys (naturally, he's a top level bowler.) Carry down does exist, but only to the extent that people are throwing plastic balls down the middle toward the headpin. It doesn't really exist in the exit area of bowlers using reactive balls. That's due to the fact that modern reactive balls flare a lot, and a fresh surface of the ball is continuously in contact with the lane.
Its very hard to train your eye to see roll out as opposed to assuming its carry down, and its even harder to convince your brain. But that's what is happening. You've carved a dry spot at your feet, and the ball is losing its hook potential before it even crosses the arrows.
As the night goes on, first you'll notice your carry getting worse. Then you'll notice your miss room disappear. It can get to the point where you feel totally lost because you have to throw a dead perfect shot to strike. Most people convince themselves that they've somehow forgotten how to bowl in the last two games. Not the case, you've just missed the move.
The next time you think you're seeing carry down, ball down. Trust me. You will see that ball get through the fronts cleaner, make a sharper move to the pocket, and once you're lined up with it you'll find your miss room and carry have returned.
Nowadays, I open bowl practice and go to Nationals every year.
USBC Open personal bests: 226/602/1690
USBC Open career average: 174.66 (45 Games)
See you in Reno 2020!