I couldn't reproduce the issue. However the old file could not be read as "corrupted" when I saved it before restarting TurboTax to complete an update. Every year there's some update, and any work I completed in March is lost.
Anyways, I'll see if the saved files can still be opened after restarting my computer. Since I saved every step along the way, maybe I'll be able to tell what portion of it was the issue. But either way, there is nothing I changed compared to when I saved my work earlier tonight (well except grouping my capital gains). Next time it asks me to update, I'll see if I can refuse the update and save my work as a PDF (for my records). Then hopefully, when the TurboTax file is inevitably shown to be corrupted upon opening it again, I can at least open it from a PDF...
