icloud contacts corrupted

A client of mine has hundreds of corrupted contacts. Both the phone numbers and the 'Country' fields have a bunch of junk appended to the original contents. Since the client is also using a Mac, the same corrupted data appears on the Mac (as well as an iPhone).

An example of a phone number is 123456789item1.X-ABLabel:Julia (note that Julia is the first name of the contact)

An example of a country name is United Statesitem2.X-ABADR:us

Many of the corrupted items show even longer 'junk' entries.

A similar posting (from a different person can be found at https://stackoverflow.com/questions/75009165/iphone-contact-details-corrupted-how-can-i-fix-them