We have looked in this internally and there are two things going on with your scenario.
First of all the update_source should be listed as Account. Since this is restoring a deleted contact this needs to be done by the account owner and not the contact themselves. The update_source would be Contact if you were restoring an unsubscribed contact.
The second issue is that there was a problem with the data for that specific contact. This has been updated in our database.
Please let us know if you continue having issues after this.
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