Trouble with Default User Access to Custom Object 3 for Editing

I am displaying Custom Object 3 as Related Information on the Opportunity record.

I cannot seem to configure so that Advanced Users can edit Custom Object 3 records they do not own. I've verified that the Advanced User role is using the Advanced User Default Access Profile.

In the Advanced User Default Access Profile, on the page for Primary access, the access for Opportunity is Read/Edit and the access for Custom Object 3 is Read/Edit/Delete.

In the Related Information section for Opportunity, for Custom Object 3 the only choices I have are Read/Create, Read,View, No Access. 

In Role Management, the Advanced User role Has Access, Can Create,and Can Read All Records for Custom Object 3.