I developed a flinch with one of my instructors a few years ago. During a moderate sparring match i got popped harder than he intended as i walked into it. From that point, my brain went into auto-defense every time i sparred him. No one else, just him.
I am not sure what padding you use, but we generally do not wear head gear as control is generally there with the higher ranks. This said, I started wearing head gear when i sparred him. Through time, I lost the flinch as the protection gave me the confidence that i had lost.
Just a thought.