Bug: When the Migrate Relationship Class geoprocessing tool is run on an attachment relationship class, attachments do not appear attached to features
The Migrate Relationship Class geoprocessing tool used to migrate Object ID-based relationships to Global ID-based relationships, causes attachments to behave as if they are not present.
In ArcMap, when using the Identify tool or editing attributes of a feature, the attachment manager displays features that have actual attachments as if attachments are disabled. If the feature does not have an actual attachment, it appears to have attachments enabled, until an attachment is added to the feature.
After the Migrate Relationship Class tool has changed the relationship from Object ID-based to Global ID-based, the attachment manager assumes that any attachment table that has the Object ID foreign key field is Object ID-based, and therefore is not using the new Global ID foreign key after the relationship class has been migrated.