Manually entered, four separate times, including with various TurboTax support folks watching.
We checked for Unmark Estimated in every possible place. Nor does the form highlight any fields not the error report in Forms show anything.
Thanks for the suggestions though. So far I've spent several hours debugging, including complete TurboTax re-install, three hours with support yesterday, another hour and a half with support today, and all they can suggest is giving up e-filing and print (which allows you proceed even if errors...unfortunately there doesn't seem to be any way to proceed with e-filing.)
