Is it only 1040 returns that have the issue?  If only 1040s:

If updating hadnt fixed it for me, my next move would have been to uninstall and reinstall the 1040 module.

You will NOT lose any of your client data files.

Use Windows Add/Remove Programs

Find PS2021 in the list and choose Unistall.  It will act like tis going to uninstall the entire program, DONT PANIC! It wont.  Once you continue, it will open a window with choices of what to uninstall.  Choose 1040 and uninstall it.   Now reopen ProSeries and choose Updates > Select and Download New Products and choose 1040 in the lower left corner.  That should reinstall the 1040 module.   If the problem persists, a full clean reinstall of the program may be necessary. 

Heres are the instructions for that, again you will not lose any client data files even on a full clean reinstall.
https://proconnect.intuit.com/community/multi-user-mode/help/uninstall-rename-and-reinstall-proserie...