Here is the process I ended up using:
1. Created a backup file
2. Repaired the game
3. Renamed the backup file to make it the official file.
4. The game complained that the file was saved in a newer version of Sims 4 and that I needed to update, but the game opened just fine.
Posting this for the benefit of others in the future. I sincerely sympathize with anyone else who is having this issue.
