Email details are being uploaded from Marketo

Drew, do you see this when you click the subject in the Activity History or in the Email tab of the Marketo Sales Insight section?  Are you seeing this with many / all of your Sales insight emails? 

I'm seeing it when I click the subject in the Activity History, and I've only seen a few of them so far. The problem is, it's tough to know how widespread the issue is.

We have experienced the same problem and put in a number of tickets. 

We've experienced the same problem as well from clicking the 'Subject' in Activity History.  By reading  Elliott's response, I decided to look at the email from Marketo Sales Insight and from there the email is visible.  It's not ideal, and not an answer to the question posed, but it's cleary a workaround.

There is a similar discussion started recenty (Email sent from the Outlook Add in Not Tracked in SFDC) where I indicated that I submitted a case to tech support and they indicated that the cause is likely invalid XML characters in the email that are preventing the email from being "uploaded" (actually creating a new SFDC email template. I did find that the email signature on at least one of our reps was full of extraneous HTML and had them replace it with a new one with minimal HTML. As I learn more I will update the newer discussion.