Hi, sorry there was a issue. There is nothing that can be done. When they (the bookmarks) are merged on the server something may have happened or that 1 of the Profiles is possible corrupted. Firefox Support Volunteers have no access to the data or to the servers or to anything other than to provide information. This is all I have on Sync : *https://support.mozilla.org/en-US/kb/how-do-i-set-sync-my-computer *https://support.mozilla.org/en-US/products/firefox/sync *https://support.mozilla.org/en-US/kb/how-do-i-choose-what-types-information-sync-firefox *https://support.mozilla.org/en-US/kb/firefox-sync-troubleshooting-and-tips *https://support.mozilla.org/en-US/kb/change-primary-email-address-firefox-accounts Suggest always have original backups : *https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles *https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer Please let us know if this solved your issue or if need further assistance.

If you use Sync then best is to disconnect Sync temporarily during troubleshooting. You can restore the bookmarks from an (older) JSON backup in the bookmarkbackups folder. *https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them The name of an automatically created JSON bookmarks backup in the bookmarkbackups folder includes a total item count (folders and separators included) and an hash value to prevent saving the same backup more than once. *bookmarks-YYYY-MM-DD_<item count>_<hash>.jsonlz4