Hi Ben! Is this happing to all your emails? If so, it might be the token you are using is not correct. Here's a Marketo article that references which interesting moment tokens to use: https://community.marketo.com/MarketoArticle?id=kA050000000KywJCAS. Hope this helps!
It happens when we add a token to populate the primary product name in the email subject line: http://screencast.com/t/rbdgzveqDkL. The token does populate with the correct info when sent, however when shown in Sales Insight the product name is not populated.
I'm finding the same problem when we use custom tokens in our email subject lines. They work in the emails, but show up as the unrendered tokens in Marketo Sales Insights. Is there a way to resolve this?