Rise: "The Custom Error Module Does Not Recognize This Error"

Hello! I'm doing some pilot Cornerstone LMS tests in Chrome, Firefox and Edge for some pretty straightforward Rise content - two lessons, one has a video and some text and the other has navigation-restricting attestation boxes to check and an Exit button that exits to the LMS - but can't get them to complete in my LMS.

This is the error I'm getting after clicking the Exit button in Rise and closing the launch page:

I don't see the content listed as Complete in my LMS. 

Only when I try the link again, re-check the boxes and exit does the Complete trigger. The error does not appear this second time (which is nice), but that's not good user experience. :)

These are my export settings:

Has anyone ever seen this error before and how'd you fix it? 

Thanks for any insight!