Thats the point. If its a restriction (or 'mistake many buyers make' which you've 'had to explain many times') then the interface for doing this is .... deficient . The cart verification logic should disallow you from completing the entire transaction if shipping isnt filled correctly for each individual vendor ( which it does for purchase fm a single vendor ) - so thanks seems its a TM site bug/deficiency the rather than vendor config or other.... And its not 'obvious when you think about it' as a) the site allows it without restriction or comment and notifies that the multi vendor transac...