I have had a few teachers receive strange errors with a Google Assignments LTI 1.3 assignment.

The assignment is created successfully.  Later, when the teacher clicks on the assignments in their module, they receive an error message (Couldn't Find Valid Settings for this Link) and their course homepage loads instead.

Some of the assignments included an embedded Google file in the rich text editor...and that prensentation's link was somehow listed in the External Tool box (under submission type).

I cannot replicate this error or fix it.  Has anyone else seen this behavior?  Any clue on causes or solutions?