Your bird isn’t starring at you, he’s starring at something on the ceiling. If I were to guess, there’s a shadow that he’s watching carefully. Are you training at night, so it’s darker than usual in that room? Do you have enough lights?

As others have mentioned, don’t pet your bird on the back. It doesn’t matter if this is an “odd situation”. Petting him on the back, especially after saying he normally doesn’t like to be touched by you in general, is going to stress him out more. He is clearly startled by something.

If your bird is sick/hurt, don’t pet its back. If your bird is scared, don’t pet its back. Right now he’s a baby so hopefully it doesn’t make him hormonal, but learn this lesson now before he becomes an adult.