I have a form with a field that does not allow duplicates (LoadID) and is mandatory.  However if I go to the record and select duplicate, the process will succeed and I will have a record with a missing LoadID, as well as the corresponding child records.

Why is this?

I can think of a handful of potential clients that may find the duplicate feature useful, but as it is, I will have to explain to all that "duplicate" can have unwanted results until such time as they go in and find the offending record and update it with a meaningful LoadID.  I would probably disallow duplicates to non-admin, but the point is, why does this succeed?  Why does it kick out the duplicate to null, then save?