While trying to sort out a model, I noticed some unexpected behaviour.
Changing the an object's primary referance mode works Ok, unless there is sample data for that object. In the later case, rather than change the object, it creates a new object with the new PRM, and leave the old one (though not visble in the diagram, it's in the object browser). I figured something was wrong after a PRM change, and errors stating a miss-match for same data, and the old PRM!
Also, if you delete the object (with the new PRM, from the diagram, the old PRM version alone remains - in the object browser. As you don't see this all in the diagram, it can be very disorientating, to say the least.
Figuring I might have selected 'Delete Shape' insteed of 'Delete object' by mistake, I ran a test in a clean diagram/.orm file with only one object. Changing the PRM worked as expected, with th object's properties being updated correctly, and in the diagram. Repeating the change after adding sample data to the object, gave the unexpected results listed above.
I then tried deleting the changed object on the diagram, and only that version was deleted, leaving the original PRM version in the object browser.