Sync eas.outlook.com contact couldn't be synced to server

[Windows Central Question]

for weeks now my wp 8.1 has had issues with sync. Emails are arriving okay, but microsoft account shows not up to date and the error "can't sync a contact", 3-4 listings for same contact. I've tried deleting account on phone and outlook.com, reset the phone, recovered from backup, no joy. Does anyone have a recommendation, please?