I think that the VIEWSTATE issue is a consequence of the _afrLoop parameter that is dynamic.
Normally the ADF framework should handle such parameter but maybe the way to extract is not the common way and so NeoLoad was not able to handle it.
Could you try to manually correlate it? That means copy that value, use the flag request feature to search that value on the server responses and if it is found create your variable extract on the flagged request.
When it's done try again to run a user validation and see if it works better.