Out of the blue, almost all of my notebooks got duplicated and the different copies contain different information. Some seem like older copies than the others. I use the linux desktop app and sometimes the Android app. I assume that the sync failed at some point and was unable to merge the two versions together.
But I'm afraid to add anything else to my notebook because if it can't properly sync 5 notebooks with only a handful of notes each, what will happen when I have hundreds of notes and I lose a ton or have to search through them all manually to fix some sync issue.
I have fixed this for now by checking all my notebooks and notes and deleting the duplicates. But this post is more to let you know of the issue in general as this has made me worry about continuing to use this software and I want to see if there is any work being done on this as I like it other than this one big critical issue.