I am having trouble with automatic gear changes in my 2019 Ford Ranger

I am having trouble with my 2019 Ford Ranger changing into first gear after it travels down a steep hill. Sometimes it changes down a gear as it goes down the hill. The problem is, the vehicle doesn't always change down to first gear when I stop at the bottom of the hill, and when I drive off, gives a loud 'clunk' as it changes into first gear on the move.

I have had it to the dealer twice. The first time they replaced the "EGR temperature sensor as per WSM." This seemed to fix the problem for a short time. The second time they had the car for nine days, and as they couldn't replicate the problem, found no solution. They even came back to the same hill with me driving and their computer connected, but it couldn't be replicated on two tries. Having had the car back for about two weeks it has done it again. Do you have any ideas on a solution?