Old Macbook MacOS Monterey 12.6.1 did a Target-disk transfer via thunderbold. New Macbook MacOS Ventura 13.2.1 - iCloud drive (all enabled) Issue: iCloud sync not uploading some files. (Sync-icon with an exclamation in its center. a Last sync status: There are items to sync. (takes a while to show this message) Tried: iCloud sync on another new user-account on the same system. Fully syncs with correct status. Both the Old and new Macbook had the issue after I tranfered/migrated the mac. What did the trick,  sudo killall bird; sudo rm -rf /Users/arno/Library/Application\ Support/CloudDocs; sudo killall bird also used some commands for seeing what happens: ps aux | grep bird ; ls -alh ~/Library/Application\ Support/CloudDocs/ At first it did not list any new files, did another killall bird.. and file where created. After this it starts a full-resync of the iCloud drive, it shows a progress-counter and ## GB of 130GB. It still froze, I used the macbook as usual, after safe-mode reboot and couple reboots it started working. Boot in safe-mode clears some old system/log-files it also fixed some slow file-copy problems  (boot safe-mode: https://support.apple.com/en-gb/guide/mac-help/mh21245/mac )