I am using iCloud app and Firefox with iCloud Bookmarks extension on Windows 10, and let Firefox bookmarks sync to Safari's on iPad via the iCloud.
My problem is bookmarks on iPad is screwed up though bookmarks on Firefox looks fine(unchanged). I deleted bookmarks of Safari on iPad but the same screwed up bookmarks were returned. I repeated but the same thing returned.
It appears that the bookmarks saved in the iCloud need to be deleted once but I could not figure out how. I googled but no solution found.