Just bumping this, since the issue persists, and is proving very irritating for instructors. To recap, we are using Shib authentication. But with it enabled, we see exactly the problem Nathan referred to:
That is, if one clicks on "Save Changes" (even if no actual changes are made) and then click on *any* other link, one gets the message
"[module] uses an external authentication system (e.g., Oncourse, CAS, Blackboard, Moodle, Canvas, etc.). Please return to system you used and try again".
Any ideas? I did try to look at the header and form data, as Nathan suggests, but don't really know what I am looking for/at.
Any help would be very welcome.