You could try cleaning the sync location and syncing afresh.
In DEVONthink’s Preferences > Sync, right-click the iCloud sync location and choose Clean Location. After the clean is rpeorted successfully in Wndow > Log, enable the databases to sync again.
Thanks for this Jim, I’ll give it a try.
Regards
Fritz
You’re welcome 
I see a lot of this messages after the upgrade to DT4beta1
I will try, what you suggest to others and will report the result
This is a five year old thread.
Are you importing emails?
No, sorry. I got the same error message, and don’t want to create unneeded posts.
Just for you to know:
- Cleaning the remote location didn’t do the trick
- I removed the corresponding files and re-added them. For now it seems to be fixed. I had some severe issues with my nextcloud due to a but in nextcloud:31 - broken server side encryption
If the error occures again, I’m going to open a new post.
I found out that those error messages were correct indeed. Those bookmarks were duplicated entries with the same UUID. Something I missed earlier.
I’ve just hit this problem. The document in question is a Markdown capture of a web page. I renamed it and filed it away using the “Move To ^C” button in the right column / sorter, then next time I looked it had returned to the global inbox. Trying to Move To again I get the “UUID already in database” error.
Looking at DTTG, I see two copies, one in the inbox without the edit, and the other where I filed it with the edit. The DTTG log says “Couldn’t delete item” for the original. If I manually delete it in DTTG and force a sync, it deletes it just fine.
So it does seem to be sync related. It’s also not a problem I’ve ever encountered before.
My sync setup is two WebDAV servers, one on a cloud VPS and the other on my home NAS.
From what browser on what OS by what mechanism, e.g., our browser extension, Share menu, etc. ?
Safari 26.2, macOS 26.2, captured using the menu bar DEVONthink icon, Capture Content from… and clicking Safari.