Users are able to create Affiliation_vod records within Sphere of Influence on iPad, including Influence_vod direction. However, the users are unable to edit the Influence_vod direction after the record has been created.
The user does not have Edit FLS to the Child_affiliation_vod field on the Affiliation_vod object.
Grant the user Edit FLS to the Child_affiliation_vod field on the Affiliation_vod object.
Please note that old Affiliation records created by the user while the issue was occurring may need to be deleted and re-created if the system contains duplicates after making this change.
CRM Help Documentation: Sphere of Influence