Tax penalty on switching job, I am shocked flabbergasted!

I had joined new org in July 2022 last year and had submitted my previous org form16 and salary slips with monthly tax deductions shown in them. Now today my tax consultant informed that since I had not submitted form 12b to new employer, the 250000 basic exemption has been counted twice and now I have to pay 30 percent of 250000 ie approx 80000 rupees!!

I don’t understand this as I was under impression that each monthly tax is being deducted and there is now way there can be shortfall in my tax deduction.

Please help me if this correct or incorrect and if it’s mistake on my part any way to reduce penalty.