Old previously removed bookmarks returned after macOS 15.6 update

After updating to macOS 15.6, old bookmarks reappeared in Safari

I just updated to macOS 15.6 and noticed that a bunch of old bookmarks suddenly reappeared on my bookmarks/favourites bar in Safari. My current bookmarks are still there, but all the old ones were added in front of them.

These old bookmarks look like they’re from sometime last year.

Has anyone else experienced this or knows why it might have happened?