If you look at individual Case, Order or Event Rego items in the admin they will rightfully show the details of the fields captured in that submission (system and custom fields) and not the live/current CRM contact data associated with the submission.
This is correct as you want to know the data that was submitted.
However, in Custom Reports, the system fields (that were part of the form), such as ‘First Name’ and ‘Last Name’ fields are pulling directly from the live CRM data and not the actual data captured from the form submission instance.
This is a problem in cases where the CRM system data is later changed, as this will change the historical report data.
Typically, you are reporting on the data submitted if you are running a report on Cases, Orders or Bookings. If you want current CRM Contact data you would report on the CRM specifically.
Ideally, when running a Custom Report, perhaps we could select either/both current CRM fields and/or form submission data fields.
Having both options may be a way to provide backwards compatibility for this issue.