Restored bookmarks keep disappearing on iMac and MacBook Pro

I needed to restore nearly all my bookmarks, which had inadvertently been deleted. After several lengthy calls with higher-level specialists, over the phone, trying to use the "Data Recovery" feature of iCloud, to no avail, I finally was able to add a back-up bookmarks file from an external drive. So, all my bookmarks and their folders finally re-appeared in the bookmarks toolbar, and I thought all was good. Well NO, it's not...

For some puzzling, and greatly aggravating reason, the bookmarks and their folders keep disappearing, with only the few that remained after most were deleted, now showing up!! What the **** is going on? I restored the bookmarks (by erasing the bookmarks plist file with only some of my bookmarks, and inserting the backed up bookmarks plist, that had nearly all my bookmarks), then at some point, maybe hours later, or after I put it to sleep and wake-up, it reverts back to the smaller folder, and nearly all my bookmarks are once again GONE!

I've deleted the smaller file then added the backed up folder, several times, both on my iMac and on my MacBook Pro, and now, they are both minus the bookmarks again!! Is iCloud doing something very, very funky? WHY IS THIS HAPPENING???

[Re-Titled by Moderator]

Original Title: Restored files keep disappearing!