[jmw1011]

This issue started for me about a year and a half ago. Deleting all my collections and recreating them worked as a temporary fix. The problem always came back after a few weeks, even if no changes were made to my collections.

I've tried different amounts of collections, experimented with differing numbers of books per collection, and tried to determine if there is a specific book that causes the problem for me. I made sure all the collection tags I use in Calibre matched what is on my Kobo and also tried just manually creating collections on the kobo. Of course I also tried factory resets, too. None of this worked.

Last summer I bought a Clara on sale hoping my collection problem would go away. The sync problem happened as soon as I set up collections and went away after I deleted them all.

The only solution I've found is to sideload all of my kobo books. I use Calibre to manage my collections and so long as they only have sideloaded books in them, I do not have sync issues. It is fine to have kobo books downloaded from the cloud on my Kobo, I just can't put them into a collection.

Edit to add: I also tried removing sideloaded books from collections, then from the device entirely. This didn't matter. It seems to be a communication problem with kobo's server. If I have even one downloaded book in a collection, sync eventually gets stuck.