Safari Bookmarks on iOS 10 & 9 not syncing with my iCloud account

Something happened to my iCloud account after I connected my iCloud account on the same mac with OS X Mojave. Then suddenly, Safari bookmarks on mobile devices running iOS 10 and 9 stopped syncing bookmarks with an iCloud account (between each other and two Macs with High Sierra). Then I checked the issue on a newly created iCloud account and logged in with it on both mobile devices and found that the bookmarks sync perfectly with the new iCloud account.

Is there a way to fix this problem staying with the same iCloud account?

If not I could switch all my Apple devices to a newly created account to solve this problem, since I could migrate some of my iCloud data to a new account. But I don't know how to transfer 16,500 songs added to iTunes from Apple Music to a new account.

Is there a way to fix the Safari bookmark syncing error that exists in my Apple account, or is there a way to completely migrate all data from one Apple ID account to another with the migration of all data, including all data stored in Apple services?

Thanks.