Safari bookmarks cleanup keeps going wacky

A couple of nights ago, I spent 6+ hours trying to clean up some of my Safari bookmarks. I have thousands of bookmarks that are many years old. Over time, they have been duplicated and scrambled up. . . possibly from old sync issues and/or attempts to sync between Safari and Chrome. Many of these bookmarks were loose and not in folders. Originally they WERE in folders, but due to past syncing issues many were dumped from their folders and were just left loose at the top level.

I wanted to take the first steps to clean up the bookmarks. I created a few new folders so that I could dump all "loose" bookmarks into a folder titled "Loose bookmarks-need to clean and sort" as well as a couple of other folders for new organization. I also spent some time deleting some bookmarks that I determined were duplicates. At the time that I finally stopped working that day, all bookmarks were contained in folders, although not completely organized yet. I still had lots of duplicates, but at least I had them better contained so that I could systematically find additional duplicates and reorganize existing folders.

I had checked on my iPhone yesterday and had not seen the changes synced to it yet. I opened up the MacBook today and many of those changes were GONE. I think when I first opened it up, I saw the still open bookmarks tab show the cleaned up list, but soon afterwards I saw many of the loose bookmarks dumped or duplicated again to the top level. The new folders that I created still seem to be there (although way down the list now), but there are again lots of loose bookmarks.

I don't know what caused the partially cleanup up bookmarks to go crazy again. I had viewed my already open Safari on my Mac Mini tonight because I wanted to see if it showed all of the clean up changes that I made a few days ago. I didn't even have a chance to really check before I glanced at the MacBook Safari bookmarks window and saw the chaos again. I don't know whether opening up the second computer's Safari caused something to happen to the "fixed" bookmarks or what.

I do have Time Machine backups, so I could restore the bookmarks file from the approximate time of the cleanup a few days ago. I haven't done that yet because I'd like to figure out what is causing the changes to NOT be permanantly saved across devices and then get scrambled again. I don't want to import the bookmarks (or swap the plist file) and then have the same thing happen again either on the MacBook or the Mac Mini.

I know that I made a LOT of changes in those 6+ hours of cleanup. Maybe that was too much for the syncing process to handle. It was just so frustrating to see all of the work go to waste.

Both the MacBook Pro and the Mac Mini are both running 15.6.1 and the iPhone is on 18.6.2. So all devices are up to date.