Will share my experience on that. I made 3 time calibration in the 6-7 years of life with Aimtrack. Yesterday, i re-calibrate and the situation where NO WAY I can finish the calibration of the 3rd action in the middle never accept it.
First thing, observe if in the calibration IR sensor you see RED or YELLOW dot. If yellow DOT, I think you are in big trouble like me.
Second, I observe that you need to help the sensibility of the IR bar to conclude this middle calibration. For myself, the only way i made it work, i share here, but please do understand it is weird, i know. I install 2 IR BAR on top of each other. And guess what...it work...why, I DONT KNOW

If i can give some less headick to someone with this trick, well, enjoy !