Why are there 2 of each document listed in "All Categories"?

Thanks for the update, @kenj, glad to hear you found the cause! If you haven't already, I recommend exploring collections: Use collections to create custom groups of vaults

As a personal example, I have some logins that are my accounts but need to be shared with some family members. Instead of having one copy in my Private vault and another in a shared vault, I use a collection to group the relevant vaults together so all the items are still visible in one place and everyone who needs access still has it. Your use case may vary, but try it out and let me know if you have any questions. 🙂