I have an iPhone 8 & X

They are both running iOS 11.4

They are both logged into the same iCloud account

contacts and everything else is synced to iCloud

When I set a custom ringtone on the iPhone X for a contact -- say John Smith, custom ringtone XYZ

then go to to iPhone 8 it will not have the XYZ rington for John Smith, so I set it to XYZ

John's ringtone then instantly changes from XYZ to random on the iPhone X

If I go and change John's customs ringtone back to XYZ on iPhone X then the John's custom ring tone changes to random on the iPhone 8

so basically you can't have a custom ring tone for a contact on 2 different phones.....anyone know why this is happening?