Stop Galaxy S7 from deleting details that I have updated for a contact, i.e. adding a new number?

[AC Question]

I have had this issue with a few of my contacts in my phone now. When I have gone to update a contacts phone number, it will allow me to update, but within 30 mins, it will revert back to the details prior to me updating them... Is it something to do with these contacts being linked to my Outlook account? I have also tried to delete contacts from my list, only to have them all reappear!

 

[DTTR]

Had the same issue.
I had a corrupt gmail account which was causing a lot of issues.
The solution was to create a new gmail account, delete all the contacts from the faulty one, leaving it without contacts for a week and then... Restoring the contacts from a backup I made.