Same ad showing up in multiple page instances

I freaking LOVE this Advertising module, but am having a problem getting different ads to show up on a single page when I use manual embed approach. I am putting this code in three times on a page, pulling what I hoped would be 3 different ads from an ad group nid=143.

[[ad|group=143|quantity=3]]

Unfortunately, I just get the same ad in each instance, i.e. three of the same ad shows up on the page. I'd like ads to be chosen randomly from the group. What am I doing wrong? (I am caching and using Boost, fwiw).