A big mistake commonly made when creating a user-defined field on a custom form is assigning the newly created field to a standard Outlook field.
When data is entered (either via the UI or imported via a ContactGenie import product), it will update the “standard” field and not the user-defined field.
For example, you are creating a new custom form and decide to create a user-defined field called “ContactNotes” that will contain <notes> for the contact. You then modify the property for this field to update the standard <notes/body> field. When the “ContactNotes” field is updated, the information will reside in the actual <Body> field (Outlook’s internal name for <Notes>).
Other variations seen related to this involve the creation of multiple user-defined fields referencing the same standard Outlook field. Doing that can end in unexpected results with information not appearing where expected.
The correct approach to designing a custom form that involves data that for a standard Outlook field is to drag the standard field to the form and not create a user-defined field.

