In the meantime this morning I contacted TurboTax support and reviewed with the rep and it appears to be a bug, and a case has been created for the tech staff to investigate. I was able to enter data in that field fine using TurboTax 2018, but in 2019 data can't be entered in that corrected cost basis field in the TurboTax interview. And therefore doesn't flow into the 1099B worksheet or the 8942 form or the places that it should affect after that.
