I have a problem similar to an unresolved post, in that the contact name keeps changing which is making a contact list column confusing.
The email address was previously also the contact name however its now become an individuals name. To correct this, I've unshared the sheet with this inbox, removed the automated notifications, removed the contact and then recreated all - still reverts from the group mailbox name of the contact to the individuals name. This is making a contact list column confusing for users.