Image Processing : Capstone Project

Hello,
I was going through the Capstone Project for "The Python Programmer Bootcamp" lesson again, and I came across an issue in the Hough circle transform section.

Well, I have the same code as typed in the lesson but instead of 8 circles, as detected in the lesson, my code detected only 3 of them.

I tried running in all possible environments, spyder, CLI, and also jupyter notebook. The results were the same. Since, I am new to image processing, could you assist me with the code to debug this?

Thanks!