As discussed with support, the current property mapping is broken and sometimes it's possible to sync a NetSuite list to a HubSpot text field and sometimes it is not working. As I suggested I think this has to do with how the HubSpot scripts are written, and it would be great if they can get fixed to include both ID's and values which can be easily done with Suitescript 2.x. When do so the connector can then map text values to text fields and ID's to List fields. Where it goes wrong at the moment is when a field contains a NetSuite Custom Record as a list rather than a NetSuite list.
As support asked me to also raise an idea here, I will refer to the ticket with # 10050954
