Thanks so much for getting back to me. I'm using a brand new Macbook Pro.
To enlarge image, I use the track pad to pinch or expand with two fingers.
It's very strange, when I enlarge the image even a little bit, the image
suddenly rotates 45 degrees to the right, enlarge a little more, it rotates
another 45 degrees and so on. Even when I reduce image size, it rotates
image 45 degrees about every 10 points I enlarge or reduce.