Understand this situation. If the unit leader doesn't want to, you can only stop the exam unless you plan to go all out to resign and go home for the exam. The stakes are a little high. I suggest you be careful.

Your work is not bad, and you have obtained a master's degree in the job. Just take it out. You don't need to take the PhD exam again, you don't need it. Do your job well, get on well with leading colleagues, and strive for upward career development. This is what you should focus on.

Personal opinion, for reference only.