vMailMergeCompany not exporting added fields


I've added a number of custom fields to the Company table but they are not coming through on merged documents, even though I've added them to the vMailMergeCompany view. The fields are avaible to select when creating the template but the data doesn't populate the merge document. 

This isn't an issue in email templates, which do bring through the custom fields. Can anyone suggest what may be causing the issue

I'm running Sage CRM 7.3.