I haven't been following this thread except addressing my latest questions these past couple days but it looks like Form 2210 has had problems, unlike most of Turbotax, which is excellent. I'm puzzled why Line 11 not including overpayment from last year still hasn't been fixed. It seems obvious that columns a) - d) should add up to be the total amount of tax you paid toward your tax liability, i.e., it should match 1040, line 33. At least it did on my last year's 2210 (TY2020). Because it didn't, the detail of 2210 showed underpayment, but (???) didn't calculate the penalty. It's like the second error cancelled out the first error.
