Thank you both for the information in this thread! I had the same problem too on my Aura One. I don't know when it started, but I can say I first noticed it on May 7th and have been too busy to investigate until now.
I can confirm that the repair function did not work for me too. Also, it could not be solved by logging in/out of Overdrive. I had to log in/out of my Kobo account to fix it. Totally annoying!