I paid for a premium account so that I could get support, and I sent in a request for support. They did respond to my message, but they were unable to solve my problem. I also tried deleting the app and data from my PC, and then reinstalling, but that still didn't work. In the end, I had to go through each of the hundreds of affected notes, individually, in the desktop app, and force it to re-sync the notes on the cloud server. To do that, I changed the note titles by adding a "0" character, then waited for the notes to sync, and then I deleted the extra character from the note titles. After that, I was able to save a backup with correct note titles in it.