Why is Turbo Tax Premier 2021 Schedule 8812 line 5 incorrect? According to IRS.gov Schedule 8812 line 5 worksheet, this should be $6000 (2 kids < 18 yo) for me not $4000

I entered my dependents as I have for the past 15  years of using Turbo Tax.  I also entered my Letter 6149 details.  Turbo Tax listed my credit in Schedule 8812 line 5 as 4000, even though the IRS.gov worksheet for Schedule 8812 Line 5 shows that it should be 6000.  The only way to correct this was to go into forms mode, select Line 5, select Edit from the menu bar then override.  Unless I'm doing something completely wrong here, this seems like a pretty bad bug that would have cost me $2000.