I believe Form 2210 Part IV Line 26 Column B (Estimated Tax Overpayment) is not working correctly due to changes related to Covid relief. All my W-2 income/withholding occurred in Jan 2020, so I check Box D in Part II. I also made estimated payments in March and June resulting in a large Overpayment on Line 26 Col A. Covid relief essentially eliminated Part IV Col B, but the overpayment from Line 26 Col A fails to rollover to Line 20 Col C. As a result TT shows underpayments in Line 25 Col C & D.
Your belief is correct. TurboTax appears to have a programming error that does not rollover overpayments from Column (a) to Column (c). No word from TurboTax as to when it will be fixed. My solution will be to use H&R Block next year. This sort of error is inexcusable.