Custom Profile fields exist on the Contact Record, so if a Supporter uses the same Contact Record when filling out a Form this may occur. If they add new information in those fields, the old information may be overwritten. If they don't add new information when filling out the Form a second time the reports will show the old information as it still exists on the Contact Record.

It is also possible that the old information will not be overwritten and this information could populate the fields in confirmation emails.

The best way to prevent this is to use Custom Event Fields instead of Custom Profile fields if Supporters will be using the same Contact Record more than once with the same fields on the Form. The Custom Event Field will attach the information to the transaction instead of the Contact Record. NOTE: Custom Event Fields appear in less reports than Custom Profile Fields. If using reports within the the event though, you will have access to report on the Custom Event Fields.