Hosted and self-hosted instances of gu-who appear to be broken?

[SteveMarshall]

Hi, I've just tried running gu-who against a test organisation both through https://gu-who.herokuapp.com and through a test instance I spun up myself on Heroku, and both error when trying to audit that organisation (URL: https://gu-who.herokuapp.com/audit/MOJ-gu-who-test) despite the app being granted the correct permissions, whether when using a pre-generated access token or using GitHub login.

The error page says “This exception has been logged with id 781o327gn.” (or similar; the ID is different every time).

Do you have any suggestions for what I might do to resolve this?