For each content_type there are settings how many thumbs to display for teasers and full nodes.
The check with 0 to suppress display of thumbs doesn't work.

In theme_node_images_view() line 556 you do

  if (isset($count) && $count === 0) return;

Unfortunately $count currently is a string, so this check doesn't work as expected.
We either have to make sure the variable is written as number, or change the check to string:

  if (isset($count) && $count === '0') return;

For now I have gone with the latter since I didn't have to touch the existing variables going that route.