I am also experiencing this problem of not being able to save a 2020 return (trying to prepare a 1040X). Windows 11 2023-07 update installed on 7/12. I ran "Repair Updates" for ProSeries 2020 earlier this afternoon (7/20/23). Still freezes when I try to save the 2020 return. I now just followed the guidance and updated the ProSeries20.ini file by using an edit in Notepad to delete the row under GlobalOptions for "LetterInvoicePrinter=Brotherxxxxxx". Closed and re-started ProSeires 2020. Problem still persists.

Apparently the "Save As" option may be the only current work-around to get a 2020 Amended return to save.