Jack, to clarify, it looks like the only field that's "getting deleted" is the "Description" field --- is this true? What kind of field is this? Is this a true Salesforce Picklist field? If so, is it a dependent picklist field? Or if it is a Text field, have you overridden its metadata type to be Picklist? Do you have any Model Actions that would be changing the value of that field if the Type field is updated?